Chrono Cross -alone- justifies the purchase of a PS2 for an console rpg'er. And it's a PS1 game!
+1. Chrono Cross is an absolutely fantastic game.
There really isn't a japanese/anime style RPG for the X-Box. The closest one style-wise is Sudeki, but it's really more of an action RPG than a traditional japanese RPG. If you pick up a PS2, however, you will have a huge
amount of RPG goodness available to you. It's worth it for the PS2 titles, but if you factor in any of the PS1 RPG's you may have missed, it's a no-brainer.