Earthbound's appeal is more charm than anything, which is really subjective. It's charmed enough people to send its price through the rough, though.
It definitely isn't a perfect RPG, and there are lots of other RPGs I'd recommend before Earthbound. It's the kind of game you play when you're looking for a different RPG, not a better one.
I'm also an RPG item hoarder, so that was my least favourite aspect. It did give it the charm of an older game, which I can appreciate. It made the early game harder, but by the end-game there's no shortage of great items, and everything else becomes vendor trash.