Looking at the top sellers from ps3 and comparing it with xbox 360 it is clear that ps3 exclusives DO NOT sell that well (compared to xbox exclusives) Here are a few examples:
Uncharted-3.10 Gears of war- 6.04mil
Uncharted2-3.13 Gears of war 2- 5.66 mil
Killzone2- 2.25 Halo 3- 10.93 mil
Resistance 2- 1.85
Halo 3 sold more than Killzone 2, Resistance and Resistance2 put together!!! Why is this?