What Engine Should I Use for My Game?

No, I’m not considering switching engines for Starcom: Nexus. This is a post oriented toward other developers, particularly new developers, who are facing decision paralysis in choosing an engine for their game.

One of the most common question on /r/gamedev is “what engine should I use for my game?” It seems to come up almost daily.

Spoiler Alert: I’m not going to tell you what engine to use. But I am going to do a survey of the engines used by popular games. Looking at quality games in your chosen genre should give you an idea what is at least possible with an engine.

Caveats:

• I’m focusing on games released on Steam, the largest market for desktop games and a likely target for solo and small developers.
• In my research I looked at a lot of games quickly and was not always able to identify the engine used for a particular title. Hopefully I didn’t mis-identify any engines.

What is a game engine? Why are they used?

A game engine is a collection of tools and software libraries that handle functionality that is common across different games. This might include: rendering graphics, physics simulation to handle movement and collisions, audio, etc. An engine allows a developer to implement common functionality very quickly without having to re-invent the wheel at every turn and allows them to focus on the features that make their game unique. They also tend to push developers toward particular development models.

Besides providing baseline functionality, most modern engines also provide a graphical editor to make creation of the game’s world and assets easier.

Fretting over which engine to use is completely understandable: once you’ve started development, changing engines becomes progressively more difficult. Not only will you have to reimplement almost all of the functionality and modify many assets, but every game engine has its unique quirks, bugs and design patterns. Changing engines means throwing that experience out and starting fresh.

So choosing which engine to use is important.

The Most Played Games on Steam

I’ll start with a list of the 50 currently most played games on Steam (as of October 2019), along with their respective engines:

Rank	Game	Engine
1	CS:GO	Source
2	Dota 2	Source 2
3	PUBG	Unreal 4
4	Destiny 2	Custom
5	Rainbow Six Siege	Custom (AnvilNext)
6	GTA V	Custom (RAGE)
7	Monster Hunter: World	Custom (MT Framework)
8	Rust	Unity
9	Team Fortress 2	Source
10	Warframe	Custom (Evolution)
11	ARK: Survival Evolved	Unreal 4
12	Football Manager 2019	???
13	Rocket League	Unreal 3
14	Sid Meier's Civilization VI	Custom
15	Source SDK Base 2013
16	Total War: Warhammer II	Custom
17	Euro Truck Simulator 2	Custom (Prism3D)
18	Garry's Mod	Source
19	Dead by Daylight	Unreal
20	Sid Meier's Civilization V	Custom
21	Hearts of Iron IV	Custom (Clausewitz)
22	Dota Underlords	Source
23	World of Tanks Blitz	Custom (CORE)
24	7 Days to Die	Unity
25	Terraria	Custom XNA
26	Cities: Skylines	Unity
27	Path of Exile	Custom(?)
28	Europa Universalis IV	Custom (Clausewitz)
29	Arma 3	Custom (Real Virtuality 4)
30	Farming Simulator 19	Custom (?)
31	The Witcher 3: Wild Hunt	Custom (REDengine)
32	War Thunder	Custom
33	Fallout 4	Custom (Creation)
34	Wallpaper Engine	???
35	Stellaris	Custom (Clausewitz)
36	Unturned	Unity
37	NBA 2K20	Custom
38	DayZ	Custom
39	Paladins	Unreal
40	The Elder Scrolls V	Custom (Creation)
41	Crusader Kings II	Custom (Clausewitz)
42	RimWorld	Unity
43	The Elder Scrolls Online	Custom
44	Stardew Valley	Custom XNA
45	Don't Starve Together	Custom
46	Counter-Strike	GoldSrc (Source Predecessor)
47	Black Desert Online	Custom (Black Desert)
48	Age of Empires II	Custom (Genie)
49	Assassin's Creed Odysssey	Custom (AnvilNext)
50	Factorio	Custom

Note: I use the term “custom” to refer to a proprietary engine developed for in-house, even if it is used on more than one title or series.

A few things jump out immediately:

1. Most of them use a custom game engine
2. Most of them were made by a AAA studio and/or were part of an existing franchise
3. The list is dominated by multiplayer games

This makes sense: AAA studios have large budgets both for development and marketing. Sequels have a built-in base audience and have existing technology to leverage. Multiplayer games have much longer playtimes than single player games.

Do not take this list as evidence that you should make a custom engine. If you’re reading this, you are probably not a AAA studio with a proprietary engine you’ve developed over years.

Also, this isn’t really a list of what you might necessarily consider “popular” games.  NBA 2K20, to pick an egregious example, has a 15% Steam review score. According to Steam 250, that makes it the 2nd most disliked game on Steam, which is not a position one would associate with “popular.” While many of the games on the list are legitimately popular, it misses many great games with finite playtimes.

The Most Popular Games on Steam

Speaking of the Steam 250, they use an algorithm that produces an alternative selection of “popular” games. You can read about it here, but in short it looks at the approval rating (% positive reviews) and the number of reviews. So a game with a 89% score out of a 1000 reviews can rank higher than a game with a 90% score out of 100 reviews.

Here are the top 50 and their respective engines:

Rank	Game	Engine
1	Portal 2	Source
2	The Witcher 3: Wild Hunt	Custom (REDEngine)
3	Terraria	XNA
4	Factorio	Custom
5	Counter-Strike	GoldSrc
6	Left 4 Dead 2	Source
7	Stardew Valley	XNA
8	The Binding of Isaac: Rebirth	Custom C++ (Based on original Flash game)
9	Portal	Source
10	Euro Truck Simulator 2	Custom (Prism3D)
11	RimWorld	Unity
12	Mount & Blade: Warband	Custom
13	Doki Doki Literature Club	Ren'Py
14	Garry's Mod	Source
15	Hotline Miami	Game Maker 7
16	BattleBlock Theater	Custom
17	South Park: The Stick of Truth	Custom
18	Life is Strange	Unreal 3
19	Half-Life 2	Source
20	Don't Starve Together	Custom
21	A Hat in Time	Unreal 3
22	Dishonored	Unreal 3
23	Don't Starve	Custom
24	One Finger Death Punch	XNA
25	Civilization V	Custom
26	The Wolf Among Us	Custom
27	Iron Snout	Game Maker
28	To The Moon	RPG Maker XP
29	Tomb Raider (2013)	Custom
30	VA-11 Hall-A	Game Maker Studio
31	Broforce	Unity
32	OneShot	RPG Maker XP
33	Undertale	Game Maker Studio
34	Counter-Strike: Source	Source
35	Katana Zero	Game Maker Studio 2
36	Mirror	Unity
37	Slay the Spire	LibGDX
38	Castle Crashers	Flash
39	FTL	Custom C++/SDL
40	Fallout: New Vegas	Custom
41	Super Hexagon	Custom
42	Eternal Senia	RPG Maker
43	The Expendabros	Unity
44	Saints Row: The Third	Custom
45	Slime Rancher	Unity
46	Half-Life	GoldSrc
47	BioShock Infinite	Unreal 3
48	Outlast	Unreal 3
49	Hollow Knight	Unity
50	The Room	Unity

At a glance, it at least looks more like a list of popular games: all the games are both well known and widely praised and clearly meet any reasonable definition for “popular game.”

Notice that almost half of them were developed using a custom engine, although Source, Unity, Unreal and Game Maker make multiple appearances each (arguably Source has an unfair advantage being Valve’s own engine).

The list is conspicuously dominated by older games, which makes sense: The algorithm favors games with lots of positive reviews. Not only have older games had longer to accumulate reviews, many of them were released during a time when there was dramatically less competition.

Powerful commercial engines have only recently become available to solo developers and small studios. Unity was released in 2005 and was MacOS only until version 3 in 2010. Unreal didn’t become available to the general public until 2009. Games often have a development cycle of several years, so the first successful games in those engines didn’t start appearing until a few years later.

The Most Popular Recent Games on Steam

Let’s look at the 25 most popular games released for 2019, 2018 and 2017. For this lists I removed free games, because in a previous analysis I discovered that price has a moderate inverse correlation with review score. I didn’t bother to remove them for the all time list because there was only one (Doki Doki Literature Club). I also added an entry for primary genre.

The notes column points out some games that are not quite free, but extremely low price, as well as NSFW entries.

Year	Rank	Game	Engine	Genre	Notes
2019	1	Katana Zero	GameMaker Studio 2	2D Platformer
2019	2	Slay the Spire	LibGDX	2D Roguelike Deckbuilder
2019	3	Resident Evil 2	Custom Resident Evil Engine	3rd Person Shooter
2019	4	Muse Dash	Unity	Rhythm
2019	5	Risk of Rain 2	Unity	3D Multiplayer Co-op Roguelike
2019	6	Bloodstained: Ritual of the Night	Unreal 4	Metroidvania
2019	7	Touhou Luna Nights	GameMaker Studio 2	2D Metroidvania
2019	8	Baba Is You	Multimedia Fusion 2	2D Puzzle
2019	9	My Friend Pedro	Unity	Shmup Platformer
2019	10	Unheard	Unity	2D Detective Puzzle
2019	11	A Short Hike	Unity	3rd Person 3D Exploration
2019	12	?? | Exception	???	2D Strategy Programming
2019	13	Streets of Rogue	Unity	Roguelike RPG
2019	14	Dungeon Munchies	Unity(?)	2D RPG
2019	15	Gorn	Unity	VR Action
2019	16	Beat Saber	Unity	VR Rhythm
2019	17	Fantasy Girl	???	Jigsaw Puzzle	$0.99, Sexual Content
2019	18	Oxygen Not Included	Unity	2D Base Building
2019	19	Supraland	Unreal 4	3D Exploration Puzzle
2019	20	Kind Words	Unity	Multiplayer Social
2019	21	Amid Evil	Unreal 4	3D FPS
2019	22	Nova Drift	GameMaker Studio 2	2D Action
2019	23	One Finger Death Punch 2	Unity	2D Beat 'Em Up
2019	24	Hypnospace Outlaw	Construct	Point And Click
2019	25	A Plague Tale: Innocence	Custom	3D Adventure
2018	1	Rimworld	Unity	2D Base Building
2018	2	Mirror	Unity	Match-3 Puzzle	$1.99, Sexual Content
2018	3	Celeste	XNA	Pixel Platformer
2018	4	Dusk	Unity	3D FPS
2018	5	Subnautica	Unity	Open World Survival
2018	6	Dead Cells	Heaps.io	Pixel Metroidvania
2018	7	Return of the Obra Dinn	Unity	Puzzle
2018	8	Gris	Unity	2D Puzzle Platformer
2018	9	Just Shapes & Beats	Unity	Rhythm
2018	10	Zup! X	???	2D Puzzle	$0.99, Achievement Hunter
2018	11	Epic Battle Fantasy 5	Flash	2D Turn-based RPG
2018	12	The Forest	Unity	First Person Survival Open World
2018	13	Nekopara Extra	KiriKiri (?)	Visual Novel	Sexual Content
2018	14	Fox Hime Zero	???	Visual Novel	Visual Novel
2018	15	Deep Rock Galactic	Unreal 4	Multiplayer FPS
2018	16	The Room Three	Unity	Puzzle
2018	17	CrossCode	Custom HTML5/Impact	2D Action RPG
2018	18	Sabbat of the Witch	KiriKiri Z (?)	Visual Novel	Sexual Content
2018	19	Miracle snack shop	???	Dating Sim	Sexual Content
2018	20	Lethal League Blaze	Unity(?)	Fighting
2018	21	Zup! 8	???	2D Puzzle	$0.99, Achievement Hunter
2018	22	Steins Gate	Custom	Visual Novel
2018	23	Super Animal Royale	Unity	Multiplayer Battle Royale
2018	24	Pit People	Custom	2D Turn-based Strategy
2018	25	Zup! S	???	2D Puzzle
2017	1	A Hat in Time	Unreal 3	3D Platformer
2017	2	Slime Rancher	Unity	3D Adventure Exploration
2017	3	Hollow Knight	Unity	Metroidvania
2017	4	Cuphead	Unity	2D Platformer
2017	5	Finding Paradise	RPG Maker XP	2D Pixel
2017	6	Hidden Star in Four Seasons	Custom	Bullet Hell
2017	7	Nekopara Vol 3	KiriKiri(?)	Visual Novel	Sexual Content
2017	8	Divinity Original Sin	Custom	3D Turn-based Coop RPG
2017	9	Gorogoa	Unity (Originally Java, ported)	2D Puzzle
2017	10	Superflight	Unity	Flightsim
2017	11	West of Loathing	Unity	RPG Adventure
2017	12	What Remains of Edith Finch	Unreal 4	First Person Adventure
2017	13	Hidden Folks	Unity	Puzzle, Hidden Object
2017	14	Opus Magnum	Custom C#	Puzzzle Programming
2017	15	OrbtXL	Unity	Puzzle	$0.99
2017	16	Rakuken	RPG Maker XP	RPG
2017	17	Planetarian HD	SiglusEngine(?)	Anime Visual Novel
2017	18	Dungeons 3	Unity	3D RTS
2017	19	Crawl	Unity	2D Local Multiplayer Dungeoncrawl
2017	20	Ravenfield	Unity	FPS
2017	21	Life is Strange: Before the Storm	Unity	3D Adventure
2017	22	Senran Kagura Estival Versus	Custom	Beat 'em up	Sexual Content
2017	23	Cat Quest	Unity	Adventure RPG
2017	24	Angels with Scaly Wings	Ren'Py	Visual Novel Dating Sim
2017	25	Monolith	GameMaker Studio	2D Bullet Hell

Two interesting things jump out immediately:

1. Far fewer recent games used custom engines.
2. Unity, which only had a handful of entries in the Top 50 all-time list, makes up nearly half the popular releases in the past 3 years.

The Major Engines

Game Maker 2

Game Maker 2 Studio is a 2D commercial engine that offers a free 30-day trial, but requires a paid license for use.

The Creator license costs $39/year and has a few limitations such as not being able to disable the splash screen or turn-off their collection of analytics data.

The Developer license costs $99, is permanent and allows disabling of the splash screen and analytics, but doesn’t cover consoles.

The Console license costs $399/year.

Development for GMS games is done using visual scripting and/or a proprietary language called GML.

Unity

Unity is a commercial engine that’s free to use but requires a paid subscription if your studio generates $100k revenue or more per year. Between $100k and $200k the “Plus” model costs $40/month per developer seat. Above $200k requires the Pro model at $125/month.

The free version is identical to the paid version in terms of core features except:

• The “dark” skin isn’t available
• It shows their splash screen in builds

This second constraint has created an odd paradox: games developed with very low budgets are forced to show the splash screen. This has created an association in the minds of players between Unity and low-quality games. Developers who can afford the Plus and Pro subscriptions don’t want the association, and remove the splash screen. Players are left with the impression that low-budget and only low budget games are made with Unity, despite the fact that Unity powers many of the most popular games on Steam.

Development for Unity games is done in C#.

Unreal

Unreal is a commercial engine that’s also free to use, but requires a 5% royalty on revenue above $3000 per calendar quarter. This royalty is calculated based on gross revenue, before any store percentage is taken out.

Epic waives this royalty for games released on their store, although the store is currently invite-only and very selective with about 100 total titles.

Development for Unreal games is done using Blueprints (Unreal’s visual scripting environment) and/or C++.

XNA

XNA isn’t exactly considered a full engine, rather it’s an environment that encapsulates many of the low-level tasks required for game development in a .NET framework by Microsoft. Development was discontinued in 2013.

Where’s Godot?

Godot is a completely free, open-source engine frequently recommended on /r/gamedev.

Development is done primarily with a custom language called GDScript, although it also supports C# and C++.

As an open-source engine, developers have complete freedom to change it however they want. Theoretically it is capable of creating great games in any genre. But so far, no popular games have been developed in it yet, leaving it in the position of its eponymous play.

The most likely reason for this is that it is playing catch-up with major commercial engines with budgets in the hundreds of millions of dollars. While it will probably never reach feature parity as long as there is such a huge budget gap, there are plenty of very popular games that do not require any of the most advanced features of Unity or Unreal.

Maybe you can be the first to create a really popular game in this engine. Even developers who don’t use Godot gain some benefit of the open-source pressure on the larger engines, encouraging progress and an accessible price point.

Custom Engine

Despite the increasing popularity of third-party game engines, there are still successful, great games being developed with in-house engines (often leveraging frameworks like SDL or Libgdx). It is beyond the scope of this post to evaluate the risks and merits of building your game without a third-party engine.

Recommendations

As I stated in the beginning, I’m not going to tell you which engine to use, but I will give a few suggestions:

• Given the huge amount of time even a modest game project takes to complete, I would advise downloading and experimenting with an engine to start, based on the genre you hope to make a game in. Do a couple tutorials. If you find the workflow not to your style, try another.
• Unity is clearly capable of making high quality games in a wide variety of genres.
• Unreal also has a large portfolio of great games. It has a reputation for being oriented towards 3D FPS games, but there are plenty of solid examples in other genres.
• Game Maker Studio has a reputation for being easy for beginners but capable enough that several very popular games have been developed in it. It is primarily designed for 2D games and its 3D capabilities are limited.
• Making a good game requires a lot of work. Powerful engines do a lot of that work for you, but it has become a Red Queen problem: they’ve enabled so many people to make games that the bar for quality keeps rising.

Regardless of the engine, expect to encounter a lot of challenges, frustration and hair-pulling bugs. If you’re not able to push through that, you’re not ready to make games. But if you are, creating an experience that brings players joy is one of the best feelings.