Why do X360 exclusives sell more than PS3 exclusives?

[Carl]

Another reason would be the Yearly Holiday bundles. At least half of Forza 2 and Forza 3s sales were bundled, for example. Halo Reach, ODST had sustained bundles too, although those are Halo so sell extremely well anyway.

To further anchor my point above, about Multiplayer Shooters and the American userbase... In the 360 top 10 there is 3 Halo games and 3 Gears games. By the end of the Year there will likely by 7 spots occupied by those 2 series'.