Starcraft will probably win if it is released this year.

Heart gold and soul silver have a shot.

Galaxy 2 won't win. I see it getting 8-9 million maybe even less than that.

halo reach for sure followed by mario galaxy. racing games aren't that popular anymore.

halo reach-12 million by years end

Out of those and this year, Halo Reach. As much as I don't want to admit, when GT comes out it will have awesome legs.

Starcraft 2

NSMB Wii. I give it a middling chance of maintaining it's pace throughout the entire year unlike the blockbuster titles that will fizzle out after a 2 or 3 weeks. So yeah.... my best selling exclusive for 2010 will be one that started selling last year.

blaatamtly reach, the halo name is too strong for the game to not sell the most, and it's becoming very likely GT5 will take ages to come to the west

Best selling, not most pirated! :P

LTD GT5 I think, looking at Prologue sales. Reach and Mario will fight for a close second, but I think GT5 will come out top in the end.

I don't see the point in counting just 2010 as you're really asking which will be more front loaded then.

I don't think GT5 sales will be bad. I mean 4mil people basically bought a beta version for the ps3. On the other hand 5mil people bought a 60$ dlc for halo 3 so reach be huge as well. Hoping mario galaxy 2 will be the first wii game I'll actually enjoy that will break 10mil. Starcraft 2 has no chance of winning due to pirating as i said before. Anyway all three will almost be very close and between GT5 and Halo reach it might depend on which console lasts longer, which will be the PS3 imo.
NSMBWii if it continues to decline as it is will sell around 7-8million this year if it gets a big boost during the holidays. Halo Reach could possibly be front loaded enough to outsell it for the year and super mario galaxy 2 will have enough time if it sells well.