Total re-edit:
Ah. OP askes top 10. I was thinking over 1m :-p
X360:
Gears 2 - 2.0m first week
Fable 2 - 800k first week
COD5 - 700k first week
Other possibilities:
Fallout 3, Banjo & Kazooie: NB.
Playstation 3:
Resistance 2
LittleBigPlanet
COD5
Wii:
Animal Crossing Wii
Wii Music
Guitar Hero: World Tour (or Rock Band 2)
Back from the dead, I'm afraid.