I can vouch for Dark Spire! I bought it a few weeks ago (off Rudy's recommendation, actually) and it's a lot of fun. It's basically like Wizardry, but completely awesome! I've even been playing it in the wireframe mode since it's faster to cruise from the dungeon and also easier to hear the "real wall/secret door" sound when you bonk into the wall.

It's LONG, too -- I guess there are only eight levels, but each one takes a while to go through (and you go up and down between them a lot). I'm about halfway done I guess.

I like the Etrian Odyssey games a lot, too. I played... well, ALMOST all the way through the first one (you get to some lame bonus levels that weren't fun so I quit) and a pretty decent chunk of the way through II as well.

I <3 dungeon crawlers... now if only someone would make a really nice DS remake of Bard's Tale, I'd be set!