I would say that at least half of Wii owners will buy Brawl at some point, maybe not launch day. Even those who bought the console in a more casual fashion probably know about SSBB and are going to pick it up eventually. You could also argue that some 75% of PS360 owners are going to pick up GTA4. (These are predictions for the Americas) In that case GTA4 will have more sales. WW, Brawl.
My Games of 2011:
The Legend of Zelda: Skyward Sword
Elder Scrolls V: Skyrim
Super Mario 3D Land
Uncharted 3: Drake's Deception