Understandably! I think I like Princess Mononoke the least of the Miyazaki films I've watched. Howl's Moving Castle, Totoro, Spirited Away, and even Porco Rosso are better than Princess Mononoke.
I like Pixar films, but I don't think any of them - even Up - compare to classic Disney. I'm not just saying that as if I grew up watching my favorite Disney movies and can't kick the nostalgia, because I didn't. I didn't watch The Little Mermaid until 2004 or 2005, and I didn't watch Beauty and the Beast until 2006, I think.
Up is very much like a Miyazaki film.