It's really what you want. PS3 has a LOT of exclusives right now:
- Infamous 1 & 2
- Uncharted 1 & 2 (Uncharted 3 is coming out soon)
- God of War 3
- Heavy Rain
- Killzone 2 & 3
- Resistance: Fall of Man, Resistance 2, and coming soon is Resistance 3
- and so on.
- Mass Effect 1
- Gears of War
- and so on (i dont have an xbox, so I don't know ALL of the exclusives, but i know PS3 has a lot)
So it's a matter of how much of the games that system has and what all your friends have.
Do you really think Sony, a competitor of Microsoft, will let you play Xbox 360? I think not, so it is VERY unlikely. I've read that you can download Android apps from the Playstation Suite on the NGP. We should get more information at E3, where I think they are going to talk about the NGP.