Why won't Ps3:s AAA games sell like Xbox 360:s?

[Simulacrum]

I bet 10€ that someone says "legs".

But when you just look at great AAA titles on Ps3 this year,against Xbox 360:s few AAA titles,they are just low as hell.

If we talk about exclusives,

PS3 has had Metal Gear Solid 4 (sold great), Resistance 2(yea europe I know),LittleBigPlanet (most hyped game of year),Motorstorm 2 (Motorstorm 1 one of best selling Ps3 game),Valkyria Crhonicles (great reviews and hype and great game),Bioshock (I know,old port),Eternal Sonata (was second most hyped game,old port as well)

Vs Xbox 360:s Ninja Gaiden 2,Fable 2,Gears of war 2.

Xbox 360 with Ninja Gaiden 2 at 0,81m (not that great),Gears of war 2 already at 3,31m,Fable 2 at 1,81m.

So why does Xbox 360:s games sell like hell in first few weeks,while Ps3:games won't sell what we thought or sales come for bundles or well they have those "legs".

Userbase?Maybe,because Ps3 is also blu-ray player.