I have looked at other systems, and they don't seem to have as diverse a game library as the XBOX. I could be wrong. I am figuring that the next generation will have a similar trend. I know that Microsoft is having 15 exclusive games - I don't know how many PS4 will have.
I have a PS3 and a 360, and I think the PS3 has the better collection of exclusive games, at least when it comes to retail games. I think 360 has a lot of exclusives through the Xbox Live Arcade, though the PSN is no slouch.
If the PS4 has some sort of online requirement I won't buy it. Which would suck because it means I won't be able to play any more of Sony's 1st party exclusive's