Disney's "The Little Mermaid" can't even be compared to this great film. A lot of people say that this film is a great visual attraction but it is so much more than that. I am 21yo and this heartwarming story glued me to the screen just as much as "Howl's Moving Castle" did. In comparison to Totoro which is also a family/kids movie, this is an even better film that will be extremely interesting definitely for all ages. When I finished watching it I felt like only 15 minutes passed or maybe 5 years, if that makes sense. Amazing!
p.s. I believe Ponyo's dad is Howl after a breakup with Sophie and a long LSD trip lol.