Best dungeon crawlers?

me too

Legend of Grimrock

Haven't really tried yet but what about Legend of Grimrock?

dungeons of dredmor

Dungeons of Dredmor. Brogue. Spelunky.

Some good recent roguelikes: https://sites.google.com/site/broguegame/

Torchlight

Dungeons of Dredmor

DIABLO 2!

Legend of Grimrock

Arx Fatalis is on sale for $2 on Steam and I hear it's a good (if a little dated) game.

I think you need to be more specific about whether you're looking for an action-RPG dungeon crawler (Diablo, Titan Quest, Torchlight, etc), a roguelike (Dungeons of Dredmore, Nethack, etc) or a classic dungeon crawler (Legend of Grimrock, Eye of the Beholder, etc)

Crawler - grimrock, it's old school and awesome.
Hack and slash.... Torchlight comes highly recommended.
Steer clear of diablo IMHO.

Desktop Dungeons is fun.

Legend of Grimrock. Hands down.

Dungeon Crawl: Stone Soup.

Really good game.