What PS2 RPG's Should I Get?

Hmm...Final Fantasy...Kingdom Hearts...StarOcean..pick one..

If you want to go with the three best RPGs on the PS2, go for FFX (good game, actually), .hack (start with Infection, if you like the story then get the rest of the series) and finally Xenosaga.

Here's some good ones:
Final Fantasy X
Final Fantasy X-2
Final Fantasy XI
Kingdom Hearts
Kingdom Hearts 2: coming soon
Star Ocean: Till The End of Time
Xenosaga
.Hack//Outbreak
Phantasy Star:coming soon
Final fantasy XII: coming soon

Everyone is suggesting Xenosaga, but if you haven't already, try Xenogears out. It's Episode 4 of the series, and in my opinion, has a better story than the Xenosagas. Be forewarned - if you're used to FMV sequences and a certain level of "realism" in your character designs, you may not like this game.

There's also Vagrant Story and like Wrath mentioned, the upcoming Final Fantasy Xll which shouldn't disappoint.