Game Maker Studio 1 and 2 aren't free, but after being purchases they do offer access to their marketplace. So if you plan on making a sonic game in 3D, game maker is out of the equation. While game maker does have the ability to create games in 3D, and there is a sonic 3D engine already released, I would not recommend using 3D in game maker as the graphics are neither nostalgic or beautiful.

There are plenty of engines already build for game maker 8, and Dazimean has taken the initiative to port his Sonic 360 engine to all the game makers. But if sharp pixels that resemble the old classic days of sonic, then game maker will be perfect. If smooth, modern quality is what you are looking for in your game, then the best engine is UE4. This does have an effect on the game as the graphics will look far smoother on UE4 than in Game Maker. Game Maker (all the Game Makers) use sprites and shades instead of models and textures. Game Maker 8 - presently updated to Game Maker Studio 2 (which is not free) - is ideal for 2D sonic games which the graphics will be that of the Mega Drive classical sonic games. (I might be a bit biased since I've used Game maker and Unreal Engine more than I have Unity). The best way to decide which of the three programs are the best is to list to pros and cons. All three have a decent sized community and plenty of tutorials that can be easily obtained on youtube. Unity isn't free, but it does make up for it by having a large Asset store. And when creating a fan game, pricing is usually the first to decide whether or not an engine/program is worth getting. Game Maker 8 ( ) and Unreal Engine 4 ( ) are two engines that are free to download. Game Maker, Unity, and Unreal are most well known game making programs, however, not all of them are free.

There are plenty of pre-made engines for many of the common game creating programs available. Depending on the idea of the sonic fan game that you want to create, picking the right engine is essential.

Sonic 3d fan game engine