Took me like 4 years to beat it when I was a kid. Although it lacks polish and good balancing, Etrian Odyssey is an original and brilliant dungeon crawler, which made the most of the Nintendo DS.
Old Eroge with dungeon crawling mechanics. It's actually a game from 1993, which, for its age, is pretty impressive. It's a really long game, so long that the NSFW content becomes secondary.