Underrated, unknown RPGs you should play:

Shenmue 2

Phantom Dust

Sudeki

Panzer Dragoon Oorta (not an rpg, but buy it anyways)

All of these would be dirt-cheap these days. Buy them before they're gone.

Between R & C and Folklore, I had to go with Folklore. R & C is a definite must-buy eventually, though like Heavenly Sword you can probably beat it in one or two solid sittings. It has tons of replay value, but personally I am very OCD about games sometimes, so RPG's (especially those with huge lists of stuff to do, like collecting every monster a la Pokemon) are a perfect fit for me. I stopped playing Halo 3 recently and I just started getting into Folklore. It's gorgeous, great fun, tons of side quests, etc. So if you're looking for a gorgeous game with more replay value than an action/platformer I'd go with Folklore.