I saw that a ton has already been said about these games, and thought I would throw my opinion out there on the ones I played, also I just posted an intro post a by here with all the PS and PS2 games I've played/own that may help you focus a list if you have any questions, some on that list I would advise away from like Forever Kingdom (LOL)
Ok so before I start I will tell you what games are my top favs so you know where my prejudice begins.
Top Rpgs:
FF7
Xenogears
FF3
Chrono Trigger
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Dragon Quest 8 - Hmm, what to say about this game, all I hear is great things about this game and I have to agree somewhat. Graphics are amazing, OST is amazing, voiceacting/story line is amazing. But you know you are in battles 80% of the game and ITS SO BORING! I literally had to give up 40hrs in because I didn't want to fight any more battles I was constantly running away hoping to get to more story. Only pick this up if you are in the mood for an Old school game.
Final Fantasy 12 - Just finished this, Plays like an MMO, you have 3 characters 2 that are autod but you can switch with them any time in battle, storyline and graphics will keep you enticed and the battles are fun, especially the hunts, however the battles can get pretty mindless aside from boss fights because so much of it is auto, but none the less a great game with a wonderful story and world to get you entertained.
Xenosaga 1,2,3 - I played the first one and was blown away at the intensity of the plot. I waited awhile before throwing in the 2nd game and watched the Xenosaga anime to remind me of the plot line. The 2nd game was pretty boring, the fighting system is medicore. Honestly, just watch the anime.
.hack series - Just played infection which took 14hrs to complete, haven't gotten around to the other 3, it was enjoyable but nothing spectatular.
SMT-Nocturne - I believe this was the one my roommate was playing which looked really fun. The graphics are a bit dated but who cares if the gameplay is awesome. This game reminded me of Jade Cocoon but with demons. If you're into those types of games, capturing monsters, morphing them, lvling them, then I would advise in getting Jade Cocoon 2, it was one of the first PS2 games, and is fantastic, the graphics and gameplay could still compete with some of todays games(for the ps2 of course)
If you have any other questions let me know!
If you want a break from rpgs, check out MGS series, DMC series or Dark Cloud 2