Isn't it because alot of Multi Platform games are developed for the 360 then they get ported the the PS3?
Current Consoles: Xbox 360 Elite, Playstation 2, Gaming Rig, Nintendo Wii, Playstation 3.
Xbox Live: Jessman_Aus - Playing: Ace Combat 6, Fifa 09
Playstation Network: Jessman_Aus - Playing: MGS4, Resistance 2
Wii Freind Code: 3513-9191-8534-3866 - Playing: SSBB
Brawl Code: 1590-6125-1250
Xfire: J3ssman - Playing: Fallout 3, Farcry 2
Jessman: Fears the Mangina