Halo 3 sale world wide currently stand at 7,861,451. If you don't count Wii sports of Wii play as real games then Halo 3 is the highest selling game of this generation. The closest game is Super Mario Galaxy which is at 6,551,976. SMG is currently behind by 1,309,475 and outselling Halo 3 by 40k per week. At this rate it would take 32 weeks.

Other possible contenders:

GTAIV(360): 5,121,624

MK Wii: 5,114,906

SSBB: 5,475,558

COD4(360): 6,023,072

Wii Fit: 4,362,327

I think it will be wii fit with its massive legs. 

im thinking SSBB cause it still hasnt launched in europe and it will help alot

I think every game you listed except for COD4 will pass it in due time. Wii Fit or GTA will be first I bet.

^if a sequesl for COD4 doesnt release this year then it will aslo have a chance to outsell halo3

Unfortunately, a sequel will be released this year. It will probaly kill off COD4 sales, even if reviews aren't that great.

 That is true, SSBB will probably be the first.

a sequel might get released,didnt activision say that they wanna make a bigger gap between the releases of teh next installments in the series

Brawl can easily make up the difference with Europe.

But I'd definitely count Wii Play and say it's the best-selling game of this generation, and the only game with a chance in hell of passing it is Wii Fit.

it would be cool if cod4 beats halo 3, cod4 is my favorite shooter

^yeah wii fit is the only one with a shot,unless miyamoto comes up with another game in the wii series that will challenge them