Fallout. I reached a point a few years back where my attitude toward most fantasy-themed games is "seen one, seen 'em all"... and the only thing that can bring me back to one is a combination of brilliant narrative and a D20 system with "all the fixins" as it were (so, AD&D 2 or 3. All of it).
I think I hit that point after I pumped a bit better than two hours into Oblivion... and just couldn't get into it. There was no direction, and nothing engaging to find, as far as I could tell... and good god was the combat boring... I knew a lot of people who absolutely loved the game, thought I was crazy when I gave up on it, but I've tried it a few times since, just to be sure... and I'm sure.
Morrowind fared a bit better. I think I lost interest after 8+ hours of play, there. I just couldn't stand the (lack of a) combat system. The rest of it was... acceptable.
Fallout 3 was a fun themepark game in which you could effectively manufacture difficulty and q necessity for combat tactics. The Fallout name was a stretch, but still, a fun game.
New Vegas should have gotten the "3", in my opinion. Fallout Themepark: District of Colombia is right there next to Fallout Tactics: BOS (or Fallout Chicago) in my book.
Going back a bit... call me crazy, but I also always preferred Fallout 1 and 2 to Daggerfall.