Sonic Adventure 2 Battle all the way, with more stages and chao abilities/skills/games/overall options as well as online capability. BTW, I'm talking more like a remake of this awesome game.
I can't believe I haven't seen Eternal Darkness: Sanity's Requiem on anyone's list. Very great game that played with your mind all the way up to the end. I can only imagine how awesome it would be on the Wii using the controls.