only reason to get a ps2 is if you enjoy NEXT GEN rpgs. but seriously if you want rpgs get a SNES or genesis or if you have a PSone thats enough.
modded xbox has an infinite rpg potential with the roms, so it blows out the ps2 even in that category imho.
ps2 has a much larger library, but its mostly shit i think. if you like playing with other people, especially with friends on the same system, xbox is where its at. if you dont know anyone serious about gaming then live will satisfy.
years down the line the ps2 will prolly be remembered as an able system but it will also be lumped alongside the psone as just an accesible main stream gaming experience. xbox, on the other hand, will prolly be recognized as one of the greatest gaming consoles ever and yes, this is largely due to its online capabilities and ROMMMMMMMMMZZZz.
the box is aging like a fine wine. ps2 struck it big then just went stagnant.