Actually here I'll post my full list of recommendations from GOG.
Outcast - More action/adventure with strong RPG elements. It's on sale for a buck fifty right now. It's really good.
Anachronox - Never played this but it's Dincrest's favorite game and Dincrest is best pony so it gets my vote.
Betrayal at Krondor - Game's old and you'll need to take notes in notepad cause it lacks an auto-journal, but the game as a whole is insanely polished, works REALLY well, had a fairly linear story with a ton of side stuff, and it's really well written.
Fallout 1 - Strategic combat. Good story. Fairly short (15 hours or so) but has no filler.
Geneforge Series - summon magical monsters to use in combat. REALLY good sci-fantasy story. Plays well. Probably Spiderweb's best thing.
Gothic 1 and 2 - Like TES games done infinitely better. Especially in terms of combat (combat is HARD and skill based), world interactivity, story-telling, and having direction.
Ultima 4-8 - Ultima 1-3 are too archaic for me to really recommend (and U2 is the worst ultima game). 4 onwards though are pretty story driven. Less apparent in 4, however 4's the start of this story arc where RPG tropes are... pretty thoroughly subverted and broken down. Combat isn't the focus in these games -- the main emphasis is on adventuring, getting information, solving puzzles... Ultima 6 and 7 have REALLY interactive worlds. Ultima 7 is a pretty ballsy take-that directed at Scientology, Electronic Arts, and organized religion.
Ultima 4 is free.
You want to use the fan-made Ultima 7 engine remake called Exult with U7, though. It fixes a lot of bugs and adds some mod support.
Worlds of Ultima - These are free too. Base don Ultima 6. One is prehistoric, one takes place on Mars and is based on Jules Verne's writing. Again,r eally cool stories, and more adventure-gamey.
Realms of the Haunting - More of an adventure/FPS hybrid and not an RPG per se but it's close enough to System Shock and Ultima Underworld to be worth mentioning, and it's just a damn excellent game in general. Acting's a bit campy, but it works. The atmosphere is FANTASTIC and the story is this really cool Lovecraftian thing.
And as I said before, Planescape. Apply the fan-made patch.
Adding steam in to the mix, I'd also recommend:
Vampire the Masquerade: Bloodlines - Story is pretty intentionally campy but it's entertaining. You definitely want to apply the fan-made patches with this, though.
Also Drakensang: The River of Time seems really good, though I haven't played it much. First Drakensang was apparently p. mediocre.
The Desolate Hope and Iffermoon. Lacking polish in some regards, but /fuck/ the thematic grandeur is something else.
Quest for Glory 2 VGA - RPG/Adventure hybrid. Delightfully bereft of the stupid shit you usually find in Sierra's games. Remake of QFG2 is freeware. You can get the other four games in the series on gog in a single pack.