Wii-18 million
xbox-23 million, I really believe that when halo 3 all the people who own a xbox will truly upgrade to the 360 and since it is so well know it will bring in million others I think Halo 3 if it has good reviews (9.5-10) it will sell 14 million copies,
PS3- 8 million I don't think it will sell much even with Lair and stuff unless it is highly commercialzed.
Basically I think for one company to win their has to be lots of commercials and good ones.