Seconding Morrowind. Man do I love that game. Sure it's a bit clunky and ugly, but some of that can be modded away. But it really is the world I fell in love with, something the later games haven't quite replicated yet. The people, the culture, all of that. It felt like a really hostile world that hated me, something alien and not your average generic European medieval fantasy world. I'll never forget my first trip from Seyda Neen to Balmora. It was dark and raining. All those weird sounds around you... Man, it just sent chills down my spine.
Yes, yes. You know of which I speak. The gameplay really was rather lacking, the conversations were repetitive and many of the characters lacked a certain... personality. I think a part of that problem was simply the large numbers of NPC's to begin with. Skyrim in particular seems rather... empty in comparison. They can't really help it, though. The company was dying, so they needed to put out a lot of stuff with a lot of options very quickly. The game did save them.
That is something you don't really get in the newer ones either. It was way more alien. Undead are always undead. But comparing bears, deer, rabbits, various large felines to cliff racers, kagouti, guar, etc..., and it's definitely going to have you paying attention at first. I remember my first trip through a... Believe it was a Dunmer Stronghold. Undead and the Corpus beasts everywhere. Ominous music, and dark hallways with occasional torches and red lights.
And, as you said, it was a harsh, unforgiving area that wanted you dead. If it's not mages lacking hindsight falling from the sky, it's the guards, and the many non-outlanders who curse you as you walk by, only refraining from cutting out your throat because then it's either jail, or death for them as well. There were issues affecting everyone. Issues with taxes, the slave trade, rotten nobles, etc... A lot of this, however, was butchered by the dialogue system either way.
Hopefully, the work from Skywind and possibly OpenMW will help alleviate some of this.