GZDoom: https://steamdb.info/tech/Engine/GZDoom/
Godot: https://steamdb.info/tech/Engine/Godot/
Love: https://steamdb.info/tech/Engine/Love2D/
FNA: https://steamdb.info/tech/Engine/FNA/
Unity 38437
Unreal 10504
GameMaker 4130
RPGMaker 2700
RenPy 1973
Godot 922
So there are 4x more games made in Unity compared to the runner-up Unreal. And both of them dwarf Godot which is the only other name I recognize in that list.RPGMaker is a piece of software that lets you make top-down JRPGs generally in the style of the 2D Final Fantasy games. Because it takes that opinionated approach it's widely considered very easy to use. You're not fiddling with e.g. a physics engine when you know what genre and style of play you're doing doesn't need it.
Likewise RenPy is designed to make it simple to build Visual Novel style games, and as the name implies it uses Python, so between using an easy, popular high level language and taking an opinionated approach tailored to one genre/playstyle, it's a highly productive and approachable engine for newcomers and indie devs with limited time.
https://steamdb.info/tech/Engine/Build/
IdTech 1-4 are all also FOSS these days:
https://steamdb.info/tech/Engine/idTech1/
https://steamdb.info/tech/Engine/idTech2/
https://steamdb.info/tech/Engine/idTech2_5/
Edit: non-commercial-only, distribution only allowed via the Internet, etc.
- Godot: https://godotengine.org/showcase/
- Löve (doesn't have a separate page, but showcases a few games at the bottom of the page): https://love2d.org
- DragonRuby: https://dragonruby.org/toolkit/game/samples
- Haxe (though not an engine per se): https://haxe.org/use-cases/games/
Zombie Age III has 10m downloads.
Deep Town: Idle Mining Tycoon has 10+m downloads (updated this year).
Space Haven is from 2020 with over 6k reviews on Steam.
(Open Source) Unciv has 6k stars: https://github.com/yairm210/Unciv
LibGDX is more low level. It's like a java wrapper around OpenGL with some nice libraries for: math/sprites/algorithms/gc-friendly data structures/other structures (octrees etc) and abstracts away platform specific details in most cases so you can have the same code for android/ios/desktop/web.
Ingress is also LibGDX, but they switched to Unity for Pokemon GO.
edit: well compositing may not occur on its own but Godot VR is a thing/easy starter
Papers Please and Dead Cells were made using Haxe with OpenFL as the framework (not completely sure).
These are only the games I've played that are built on FOSS engines. I'm sure there are many more.
https://torque3d.org was used on Airship Dragoon, Marble Blast Gold, Penny Arcade Adventures, Legions: Overdrive and descends from the original Tribes engine.
Hellbreaker, Bit Champs with https://u3d.io
And plenty of successful games with Ogre, including Torchlight: https://www.ogre3d.org/showcase
[1]: https://libgdx.com/
It’s not perfect because some engines (like Godot) have export options to bundle games into a single executable that SteamDB can’t use for engine detection.
If you are wondering what modern open source engine to use, Godot seems to be it. If you are wondering if any FOSS engines ship games, the answer is an overwhelming yes. If you are wondering how to write an engine, any of these OSS engines will teach you what you need to know (or at least get you going).
https://github.com/ConfettiFX/The-Forge was used in No Man's Sky, Hades and Starfield.
https://github.com/jrouwe/JoltPhysics is the physics engine in Horizon Forbidden West.