Yeah, I can see how this one became a cult classic. For an NES release, and not even a particularly late one all things considered, it just has so much charm and atmosphere. The creative use of the magic spells is what did it for me. Telepathy lets you communicate with the four wise men whenever you want, mostly for hints but it also fleshes them out as characters quite a bit. The disguise spell is used for various puzzles but you can also wander the towns in different forms to get flavor text that really helps the world feel more dynamic. These two spells combined with fun characters, setting, and story create an experience I have yet to see any other NES game come close to.
Some of the puzzles were very annoying though, particularly one where you have to use the paralysis spell on a random NPC and then talk to them. The hints from the wise men mention this but have nothing to say about which NPC to use it on. Overall the experience was excellent, though.

R.I.P. Stom, forever in our hearts