I've been wracking my brain trying to think of something newbie-friendly for your first playthrough, but I'm having a hard time coming up with any that are particularly approachable to someone who doesn't already know what a dungeon crawler is...I think the answer might be a hybrid-genre series like Persona. The Persona Q games are explicitly first-person dungeon crawlers, so if you've played some of the main Persona games and you want to give a dungeon crawler a try, maybe try PQ or PQ2?

But that doesn't really answer your question about the ABSOLUTE BEST dungeon crawlers though. To me, the gold standard is Etrian Odyssey, which might also be a good starting point: it has a relatively modern ruleset and plays pretty much how you'd expect a standard JRPG to play. It's very easy to pick up and play and is challenging without requiring that you learn a whole new (old) system like THAC0, which Etrian Odyssey's sibling Dark Spire uses, or many of the dungeon crawler games that hew closer to Wizardry.

All that said, the games I think are the tops of the tops are: 7th Dragon (DS), 7th Dragon 2020 (PSP), Shin Megami Tensei: Strange Journey (DS/3DS), Etrian Odyssey series (DS/3DS), Dark Spire (DS), Undernauts: Labyrinth of Yomi (PS4, Switch, PC). Runner-ups for hybrid visual novel/dungeon crawlers are Ray Gigant (PS Vita) and Zanki Zero: Last Beginning (PS4, PS Vita, PC).

Also, honorable mention to Dungeon Encounters, which doesn't really resemble any of the other games I mentioned but is a 100-floor dungeon crawler at its core. It's very minimalist in both presentation and rules, so I think it'd be hard to use it as a stepping stone to the other games mentioned, but it's definitely worth checking out in any case.