That's because it's Miyazaki. Miyazaki is the anime equivelant of Pixar - there's something for everyone to enjoy.
Pixar is awesome and all, but they really aren't in the same league as Miyazaki. And John Lasseter agrees with me.
Howl's Moving Castle is not the best Miyazaki movie by a long shot but it's still better than pretty much any animated feature not by Miyazaki from the past 10 years.
See, quality is not at all the comparison I tried to make. I meant as in both their animated movies are almost universally well-liked because everyone can find something enjoyable in them. (Although I have to say that yes, while Miyazaki is usually way out of Pixar's league, Pixar has it's moments of triumph. For example, the first segment of Up goes toe to toe with anything Miyazaki has to offer IMO).
I have to admit though, Princess Mononoke is my favourite animated feature of all time.
(Also, I agree with Pidesco, including the part about Grave of the Fireflies. Be warned though, that film has brought many a grown man to outright weeping!)
I definitely agree about Up. The introductory segment about Carl's life was quite simply magical. Up is just a bit disappointing after it turns into action adventure mode. A similar thing happened with Wall-e. Anyway, Pixar's animation skills are nothing short of awesome. The bird in Up, for example, was incredible.
I am not ashamed to say that Grave of the Fireflies had me crying like a little girl.