The game that put Blizzard on the map was the ultimate dungeon-diver's wet-dream: it sent you through no fewer than 16 dungeons, on your quest to enter hell itself. Which, of course, was fantastically good fun. But the main reason behind the game's phenomenal success was that it paved the way for WoW by encouraging groups of players to matchmake and hack-n-slash their way through those dungeons co-operatively. Without doubt one of the games that changed the world. A world that still awaits Diablo III - come on Blizzard, pull your fingers out...
14. Ultima Underworld
Ultima Underworld's subtitle - The Stygian Abyss - gave an inkling that it might be heavy on the dungeons, and indeed it didn't disappoint on that front. The first Ultima game without any input from Richard Garriott (although Warren Spector was involved as producer), it was also the first proper RPG with a first-person perspective. In other words, it's a great big slab of dungeon history. The likes of Ken Levine and CliffyB have cited it as an influence. Years ahead of its time.
15. Dungeon Master
Time to head back to the Stone Age of videogames: 1987, to be precise. A time when RPGs were turn-based and graphics resembled bad ASCII art. But not Dungeon Master. Released for the mighty Atari ST (it was the ST's best-selling game ever), it broke ground by being both real-time and 3D (after a fashion). If you're looking for the point at which RPGs as we know them were born, then Dungeon Master is it - its influence has been acknowledged by a number of faithful fan-made ports to more modern platforms. Given that Dungeon Master's dungeons were the first ones that actually looked convincing (and therefore possessed that essential scuzzy atmosphere), you could argue that all of those dungeons you've trawled over the years could be traced back to here.