As the supply constraints drop and more Wii's get into more hands, the sales of Wii Fit will rise. More Wii's will be sold, and so will Wii Fit so I think it has a hell of a shot beating just about anything.
My Games of 2011:
The Legend of Zelda: Skyward Sword
Elder Scrolls V: Skyrim
Super Mario 3D Land
Uncharted 3: Drake's Deception