I recommend Knights of the Old Republic. The first one. It's amazing, well written, yet very simple, but that actually makes it better.
The second game is good too, but as usual for Obsidian, it's a largely unfinished game, which is sad. I love the characters and the gameplay in that one a lot, even though I hate the starting area.

I would love to recommend Neverwinter Nights 2, but sadly even on my high end gaming PC, it manages to be very annoying. NPC AI is very dumb, the game is a buggy mess, companion characters are barely fleshed out, the main story is kinda good, but the first (and longest) act of the game is a snorefest. The Mask of the Betrayer Expansion however is worth playing, it's one of the best D&D games you will ever find.

I also recommend Tyranny, it's the game that Pillars of Eternity should have been. It's rather short, but the combat and the story are both very satifying, the companion characters are interesting, and you get to make choices that actually matter in the end. I want to give special kudos to Tyranny because all companions have their own skill trees that reflect their own personal backgrounds and I just love it to bits. Rally goes to show how you don't really need a class system to make a good RPG.