The Etrian Odyssey series is really friendly as everyone says. It's not easy, but it's pretty smooth (as long as you're smart about team-building). My favorite is III, but they're all good. If you like those and want more, check out the Persona Q and Labyrinth of Touhou games.
People also like the mainline Shin Megami Tensei games, though only some are dungeon crawlers, and they have more of a JRPG structure. The first has a great PS1 port, the second is on the SNES, Strange Journey is on DS, and IV, Soul Hackers, and Apocalypse are on 3DS. Artificial Dream in Arcadia is an SMT-inspired indie.
I've heard that Labyrinth of Refrain and Labyrinth of Galleria are pretty accessible. Zanki Zero has a unique setting and concept for the genre. Experience (the studio) has made a bunch of dungeon crawlers, like Undernauts and Labyrinth of Zangetsu, but they are more punishing/demanding. Same with the Elminage series, which has only rarely been localized.
There are also a bunch of dungeon crawlers that got their start on the PSP/Vita, like Class of Heroes, 7th Dragon, Demon Gaze, Mary Skelter, Dungeon Travellers. Most of these are very anime, some are pretty horny as well. Many have been ported elsewhere.
Then if you want to get more intense, there's Wizardry, the grandaddy of dungeon crawlers, of which you could try Wizardry 8 or Tale of the Forsaken Land on PS2. There are other old series like Eye of the Beholder and Might & Magic which I don't have experience with. The more recent Grimoire is considered a "boomer dungeon crawler," sort of like a "boomer shooter" I guess.
Some outliers: Wizardry Variants: Daphne is a pretty decent gacha phone game. And Wizardry Online is a defunct online game that some fans are trying to bring back.
Finally, there's also the world of real-time dungeon crawlers, which are a whole other beast. Those include Ultima Underworld, Legend of Grimrock, Fromsoft's pre-Souls games, and some indies like Lunacid.