Magic set atmosphere
This movie is just awesome.
Other than writing, directing, acting, cinematography, editing being perfect, what I find elevates it above most other great movies is the thick atmosphere it exudes:
every shot feels like they really are in a scary/funny castle/transilvanian village (you can almost smell the dust/humidity of the castle) and never feels like a set.
Above all, you can tell that the cast had exceptional chemistry, and that they were having a lot of fun being these characters and living in that atmosphere. I think this is its secret.