PS2 Has a lot of REALLY good exclusives and has backwards compatibility if you are into PS1 games. Also, people seem to forget how awful the original xbox controller was, it was the xbox360 that put xbox controllers above PS controllers.
Honestly its entirely up to what games you enjoy the most.
For me, I play Final Fantasy 10 and 12, Metal Gear Solid series (MGS2 is on xbox, but 3 is where its at), and Rachet and Clank, which iirc are PS2 exclusive (When compared to xbox)
On the other hand, xbox has halo, though is graphically outdated and lacking multiplayer.