There are a lot of good RPGs for the PS2. I can list some for you.

.hack games (1-4 and GU 1-3): These games have a pretty good story and are fun to play, but each game is pretty short. Each game is probably only 20-30 hours long to complete and the stories are continued in the next game, so you would need to buy the first four or the three GU games in order to play through a whole story.

Xenosage 1-3: These games are also very good. I love the story and the battles are pretty fun. Again the story is carried through all three games, so you would need to buy all three to play through the whole story.

Disgaea: Hour of Darkness: This is game a pretty good strategy RPG. I don't really like the story that much, but if you like strategy RPGs, you would probably like this game.

Kingdom Hearts 1-2: These games are also pretty fun. I like the battle system because it is more interactive than most games and the story is alright. Unlike the other games I mentioned, you could play the first game without playing the second game, but you would probably want to play the first game first if you are going to play the second game.

Final Fantasy X, X-2, XII: These are all good games, but I think Final Fantasy X is the best out of them.

There are also plenty of really good Playstation games that are very good, if you are willing to get them. You can find a lot of these games at a fairly reasonable price, but some have become hard to find already.