I love "nice" monsters.
I love movies where the monsters are NICE and CUTE and LOVING and HEROIC.
Monsters inc and monsters vs aliens and hotel transylvania are good examples.
The Water horse about a boy in Ireland befriending the Loch Ness monster was a BEAUTIFUL movie.
Maybe it has to do with the contrast. "monsters" by definition are supposed to be evil scary murderous hideous beings so when a monster is the opposite of that it is a refreshing change.