Why do X360 exclusives sell more than PS3 exclusives?

[walsufnir]

maverick40 said:
it is simple. There are more ps3 exclusive games than 360 so the ps3 gamer has more of a choice.

and because all of these great exclusives, ps3-owners can't decide which game to buy and decide to not buy games - or how can more exclusives result in a worse software:hardware-ratio?