I want to make a "fangame" but I don't know which engine to choose. The style of the game is the same as Sonic 2 HD.
Thanks :)You can choose any 2D Sonic engine that you want and just change the sprites to the S2HD one. Make sure you credit the S2HD team!
But for the engine itself, Gmate and Sonic Max uses GameMaker Studio which has a free version but you can't share the project to people, but you can buy $9.99 per month or $99.99 per year so you can share the project to Desktop, Web and Mobile.
Sonic Worlds uses Clickteam Fusion which has a free version but you can only share it as a web game, not an .exe. But if you want to share it, you have to pay $99.99