I absolutely loved this movie, but then again, I think http://en.wikipedia.org/wiki/Hayao_Miyazaki is a genius, and I absolutely love everything he does.
So for me, i'd have to say Spirited Away, Princess Mononoke, and My neighbor Totoro are my favorite movies. I realize i'v stuck my head in the sand here with just one genre of movies, however I think these, personally, outweigh everything else i'v ever watched.