Fantastically epic game that's why, although I have to say those numbers are a bit off, as I saw a 119 900+ (Currently 104 000+) people playing MW3 on launch, according to the game's in game player counter. The only thing is the MW3 players will continue to grow or at least maintain that lvl for awhile where Skyrim will start losing players within a week, as people finish the main story.
Still epic though +1 Bethesda
Diablo III will probably have in excess of 400 000 on launch...when it finally launches..lol