I have to recommend Ultima Underworld too. It's pretty old, but it's actually one of my favorite games ever (tied with Torment, but for entirely different reasons). It was a big inspiration for the Elder Scrolls and System Shock/Bioshock games, yet it's better than all of them (IMO of course).

Also, you mentioned that the only NWN2 expansion you've played is MotB. If you're not completely burned out on D&D and enjoyed the Icewind Dale games, it might be worth your time to give Storm of Zehir a try. I personnaly loved it. It's not all that long, and it's light on story, but I found walking around on the overland map, discovering new locations to be very enjoyable. Some of the fights were also pretty fun, or at least better than anything else I've seen in the Neverwinter Nights games (Although HotU had some pretty fun fights too).

Edit: hadn't seen JudasIscariot Ultima Underworld recommandation, sorry!

Look here.

* The Pool of Radiance Forgotten Realms series (developed internally at SSI):
o Pool of Radiance (1988)
o Curse of the Azure Bonds (1989)
o Secret of the Silver Blades (1990)
o Pools of Darkness (1991)
o Forgotten Realms Unlimited Adventures (1993)

* The Savage Frontier Forgotten Realms series (developed by Stormfront Studios):
o Gateway to the Savage Frontier (1991)
o Treasures of the Savage Frontier (1992)
o Neverwinter Nights, the first graphical MMORPG, for AOL (1991)

* The Dragonlance series (developed internally at SSI):
o Champions of Krynn (1990)
o Death Knights of Krynn (1991)
o The Dark Queen of Krynn (1992)

* The Buck Rogers series:
o Countdown to Doomsday (1990)
o Matrix Cubed (1992)

Additionally, Spelljammer: Pirates of Realmspace (1992) used the Gold Box combat engine.

I would give Divinity 2 with the FOV add on a try - I am completely enjoying it and I bet you would too.

Mage Knight Apocalypse, this is fun exciting and quirky as he'll... It's just fun... Also Dungeon Siege 1 and 2 they're long and absolutely fantastic I recommend them very highly.... If you want torchlight drm free get the box from encore and you can install infinitely no limits and no call home.

Speaking of Dungeon SIege, don't forget that Dungeon Siege 1 has a mod called Lazarus:Ultima 5 which is a Total Conversion and allows you to play a very beautifully rendered Ultima 5. For free!

Has the king bounty series been mentioned?

I would strongly recommend to to play them in order, as you can transfer your party through the games and Roa 1 has some of the best equipment in the whole series. And many people claim Roa 1 as the best of the series. Additionally each game plays significantly different in an "overall" kind of way ...

Are you referring to the Official Campaign of NWN? I know lots of people who got bored with that halfway through (myself included) and they had years of fun playing NWN nevertheless. Don't underestimate the community modules, all the praise that NWN still gets after all these years certainly isn't only due to the Official Campaign - if at all (although the add-on Hordes of the Underdark was pretty good, too).

NWN modules are not like like mods in other games that only make modifications to the Official Campaign. They're self-contained RPGs, each with its very own plot, and some even with different rulesets and gameplay. Most of them are a lot better and totally difefrent than the Official Campaign. With NWN (and preferably its two expansions) it's highly unlikely that you'll run out of RPG's to play because there are literally thousands of modules for it; of course not all of them are really worth playing but dozens or even more than a hundred are (and that's only counting the single player campaigns).

I recommend checking out the Prophet series or excrucio eternum, for example.

(Btw, to a smaller extent the same goes for SSI's "Forgotten Realms Unlimited Adventures" included in the Goldbox package, if you should ever get your hands on it. Lots of great and free to download community modules that surpass the campaign that was shipped with it, too).

***

On a different note, "Nox" is a pretty nice Action-RPG that I believe hasn't been mentioned here yet.