Daggerfall remains the one game I play most. It only took about 5-6 months after
Oblivion's release before it returned to being the TES game I play most. Chances are good that barring the first week,
Skyrim (whenever I finally do get it) won't displace DF.
Daggerfall is the only TES game that really made you relieved seeing daylight after spending hours inside the bowels of a dungeon.
In all honesty, I'll admit that I got some of the same feeling from
Morrowind's Arkngthand, though that was really only the first time I played it, and of course, that's but a single dungeon. The rest of the game's dungeons were way too small.
I don't mind sprawling as long as it's 2D with a map that is actually useful.
I will grant that the very, VERY 3D nature of the maps lent exponentially to the ease of getting lost... It gets easier once you figure out the module-based nature of each map, which does tend to break the thing down into much more manageable chunks.
And of course, there are SOME particular 3D portions I'd never give up; some of the very tall chambers yielded much more interesting gameplay than I'd ever see with just flat 2D passages. Though the "spaghetti" sections... Yeah, the game probably would've been less headache-inducing without them.