A short list seeing how I haven't completed many,
Skies of Arcadia, I don't know why but it was one of the few RPGs to capture my attention. I realize that is does pretty much everything a normal RPG does, but I just loved the setting and the characters.
Pokemon, its an addiction, there's no way around it, and I will catch em all again.
Paper Mario/Mario and Luigi, I'll put them here not to clutter the list. I love Mario, these games are fairly fun RPGs and not too complex so I enjoy them.
Baten Kaitos, I didn't think a card RPG would hold my attention but it really did. With such a fun and fast battle system that kept you thinking, an interesting dynamic plotwise.
Semi-RPGs like Borderlands and Mass Effect I guess.