This may have been true last gen, but the libraries are pretty wide open. Action games, RPGs, things other than 'FPS' are pretty prevalent on both systems. In fact, it's kind of odd this gen in that a brunt of PS3's big titles are FPS games. I really don't see how someone can find 'nothing to play' on either system.
Not only that, but but playing Live with your other man-child friends can get very viral to peer pressure other friends into buying one.
If I have time to play games online with other's and paying for it I'd play WOW. I agree with Rokkit that there is a little for everybody this gen in both systems. I do believe that as a gaming device 360 and PS3 are pretty much similar. That said, I bought a PS3 for the Blu-Ray player. I disagree with Rhino on the notion that 360 >>>> PS3.