Aye, I have played Divine Divinity and Beyond Divinity. There are a few games on GOG which I have not played yet, namely Invictus, Ishar (which I heard has a rather tedious save system, as it punishes you for saving), Might & magic 8+, Robinson's requiem & Stonekeep. Steam sadly seem to flood their categories with games that really don't belong in their respective category (Delve deeper might be a good game, but it is absolutely not an RPG).
I have played Bioshock, but Chronicles of Riddick was a bit too demanding for my computer when it was first released. I've heard a lot of good things about the game, and Dark Athena apparently contains both the original game and a brand new campaign (which is supposed to be quite a bit worse than the original). While not an RPG, I should probably check it out, I remember being interested in it when the original was released.