(Sega Dreamcast) Sonic Adventure 2

I love this game. You can choose which side to play as in story mode. (Hero or Dark) This is the first game in which Shadow the hedgehog appears. Also you can play with a Chao and raise them and you can play 4-player chao race or 2-player chao karate. Also you can play 2-player racing as Sonic, Shadow, Amy, or Metal Sonic and many more modes like shooting battle and treasure hunt.
Almost Every Sonic fan has played this game.