I’m finally going to pick up a PlayStation 2 and catch up on all the RPGs I missed-- basically everything except Final Fantasy X, which I played on a friend’s system back when it came out. I’ve already picked up, or am planning to get, Final Fantasy XII, Final Fantasy X-2, Wild ARMs 3 and 5, Dragon Quest VIII, Grandia III, and Xenosaga Episode III. I’ll probably also get Wild ARMs 4 to round out the series, although it seems to be less well liked than the others.
Any other recommendations?
Don’t miss the often overlooked Shadow Hearts series - it’s a Lovecraft-influenced WWI-era RPG series that’s excellent. The first one is harder to find than the other two, and part two - “Covenant” - is the best out of the series.
The just-released Persona 3 is amazing.
It’s a bit old-fashioned, but I’m really fond of the Breath of Fire series, especially III.
Suikoden V is good, though if you want all the characters and the best ending you need (100% need) a guide (though you can get them online).
Final Fantasy X-2 is skipable. To be more harsh, it’s a quickie cash grab by Square-Enix that plays horribly and is packed with some of the biggest nonsense ever put into a Japanese RPG (and considering the competition that’s an accomplishment).
I’ve always had a soft spot for the Suikoden series myself since I enjoy the collecting characters aspect of it. If you’re interested in something a bit more tactical the Disgaea series is interesting. And finally if you and three friends want an action/RPG the Champions of Norath series have a nice balance to them.
Eh, it looks pretty fun to me, and for a whopping investment of $12.99 (new), I won’t be too upset if I don’t like it. 
The investment isn’t the money, it’s the time. I spent accumulated weeks of time on FFX, I spent maybe an hour on X-2 before deciding it was not worth the effort.
Kingdom Hearts is a good game, as long as you can ignore the melodramatic nonsensical storyline. It’s basically like Final Fantasy, with most of the familiar items and spells, but it’s an action-RPG so you hit stuff and select magic spells on the fly during battle, and you have Disney characters as your party members. I’m not really a huge fan of either Final Fantasy games or Disney movies but the game itself was pretty fun, and the soundtrack is awesome.
I liked the first game well enough, although I found the “Judgment Ring” system very annoying. You have to time your button presses to an indicator on the screen to do pretty much anything other than walk around or look at your menus. The sequel went way overboard with juvenile innuendo, and didn’t have characters so much as caricatures.
Baldur’s Gate: Dark Alliance I and II were pretty good action/RPG games. Don’t expect them to have anything in common with the regular Baldur’s Gate series though. Dark Cloud I and II were also good, but a bit repetitive at times.
For tactical RPGs, Front Mission 4 is excellent. You switch between two different squads of mecha (called Wanzers in this universe) from opposing factions as they try to figure out what’s going on. The mecha and pilot skills are highly customizable, although it’s best to improve on the skill set that a given pilot starts with rather than try to completely change their role (don’t try to make the mechanic into a sniper, for instance).
I’m a Final Fantasy whore, so those are always good, but if you’re looking for something a little different, I really enjoyed Star Ocean: Till the End of Time. Great plot and story telling, not too horrible humor, good battle mechanics, and a healthy amount of gameplay made it a great game.
Oh, and The Bard’s Tale is good bawdy fun. I doesn’t have great graphics, and it’s more of a hack and slash, but damn it was really fun to play. And that’s what matters.
Awesome game, until the Last Plot Twist, which will make you want to pound your head into a wall. Just fair warning. 
I’ve almost bought this from the used game store about 10 times before changing my mind. Now I’ll have to get it.
Champions of Norrath, and its lovely sequel, Champions: Return to Arms. These games have extraordinary replay value and are loads of hack-n-slash fun. You can import your old characters into the sequel and level them up even more, with new skills, as well as explore the availability of new characters.
Kingdom Hearts is surprisingly fun and difficult, and, believe it or not, the Lord of the Rings RPG is actually a pretty solid game.
I’ll be watching this thread carefully…
You MUST, you absolutely MUST play this game. Hilarious.
Oooh, I almost forgot: the gargoyle game… Primal. Very fun puzzle and RPG game, I loved it.
That’s where I got it. It’s relatively short (compared to Star Ocean) and not a great amount of replay value, but it was thoroughly enjoyable.
I actually thought it was interesting. I’ve played enough RPG’s that I liked it alot that a) there was one and b) it wasn’t a cliche. But I could see how it might be frustrating to someone else.
Okami is a game that shouldn’t be missed. It plays more like a Legend of Zelda title than a traditional RPG though.
Both were fun games, but they were both released on Playstation, not Playstation 2. Not a big deal, obviously, with backwards compatibility, but might have made it harder to find the games.
I really enjoyed La Pucelle Tactics. A nice tactical RPG with a colorful storyline and absolutely ridiculous characters. It’s probably pretty hard to find, but worth every penny.
Ignore it’s pseudo-sequel Phantom Brave. Not nearly as much fun and I’m actually not sure why I didn’t sell it off a long time ago.
I really dug Beyond Good and Evil. It’s kind of short, and not very challenging, but it is charming and fun. And it’s pretty cheap to pick up used.
Deus Ex is also available for the PS2. It was great on the PC.