Disgaea 2 Nippon Ichi sucks.
Shin Megami Tensei: Digital Devil Saga One of the best ps2 rpgs. It's MegaTen. If you don't pick it up now, get it eventually.
Shin Megami Tensei: Digital Devil Saga 2 Better in many ways than the first one
Outrun 2006: Coast 2 Coast Really good
Yakuza Pretty good. Suggested.
Onimusha: Dawn of Dreams It's decent.
Suikoden V If you're looking for a pretty good traditional rpg for the ps2 that isn't Dragon Quest VIII, this would be my suggestion.
Shin Megami Tensei Devil Summoner: Raido Kuzunoha It's a very unique and experimental game, but many of its experimentations are flawed and not fully developed. It mixes adventure game elements with traditoinal rpg gameplay with an action rpg battle system and a MegaTen twist. The adventure elements make it feel unique, and I wouldn't mind a more fleshed out sequel. It's worth checking out, if not only to experience it but it shouldn't really be on anyone's priority list.
Breath of Fire V: Dragon Quarter At the current point in time, this is by far the best ps2 rpg, and best rpg of last gen period. It has one of the most innovative rpg designs in the last 10 years, and is very very underappreciated. With that said, it takes someone who's eager enough to "get" it, but once you do, it is unrivaled. The battle system is balance and varied as shit, offering an amazing amount of depth and skill that not only fixes many jrpg problems, but but outdoes many of them on several levels. For example, there's only 3 characters in the game but each has a unique ability. Take your gunner for instance; if you want to, you can use her to kill weak enemies from afar, making it so you don't have to engage enemies weaker than yourself. The battle system itself is a mixture of strategy rpg and turn based combat. It is to be described as a survival horror rpg, and that is the absolute best description one can give the game. Absolutely daring, fresh, and ballsy, Dragon Quarter is highly suggested.