I recently injured my ankle while traveling in Vietnam and decided to learn some Lua by writing a roguelike.
I discovered that the 'best' (most complex/featuresome/interesting/interactive/playable) dungeons available today are apparently almost universally accepted by the roguelike community to be those in the game Brogue, which I was so impressed with that I tried to share here twice but it never got upvoted. It's really impressive, check it out: https://sites.google.com/site/broguegame/
Why is it impressive? As it turns out, modern dungeon generation does not simply produce a map, but rather iteratively improves upon a map given assumptions around playability (minimum connectivity / maximum dead-ends), density (don't put all the interesting stuff in a corner), proximity (some things must occur near other things), etc.