I second Okami, it may be "childish" but it's still a beautiful and very fun game.

However, as was mentioned upthread, without having any idea of what games you like it's hard to make recommendations.

For PS2 RPGs, besides the standard Final Fantasy games, I offer Tales of the Abyss and Dragon Quest VIII: Journey of the Cursed King. Tales has a more action-based combat system. I loved the characters more than anything else. The story was good with lots of character development, but ended up becoming really weird near the end. Still a worthy choice though. DQVIII is sadly a much overlooked game, as most people bought it solely for the FFXII demo. Shame on them. It's a very classic style RPG, tougher than the average Final Fantasy and with a lot more charm. The story is a great example of a simple one done very well, so while you may not find a lot of depth, there is a lot of heart.

I've waved my favoritism banner for the day, but I'll try to come back and add more targeted recommendations once I know what you're looking for.

~DragonHeart~