Animation, by and large, started out targeted at every one. I mean you look at the old Disney and Looney Tunes animations and you'll find references to political figures, **28**, or adult jokes that little children wouldn't get. Somewhere along the line, animation got simpler and more childlike, and now we have this attitude that "Cartoons are for children." There are many great animators in America, but sadly they do not work for major companies so they are not well known. (Bill Plympton comes to mind) The Japanese school does indeed have great backgrounds, even in television shows, though the sad thing is when you look at the older American titles by Warner Brothers they have just as excellent backgrounds as well. It's a pity to think somewhere along the line that we lost it.
In terms of actual animation itself, Japanese seems to be more limited than American. The reason I can think of is perhaps Japan did not evolve with the "12 Principles of Animation" that American animation developed with, namely the principles of squatch and stretch, anticipation, etc. One thing I forgive Japanese animation for is that many of their titles are based around a story, so the animation may not even be important - in fact, sometimes I think American animation could learn from the fact that your characters can sit still and be effective and not "milking the giant cow."

However, people often mistake fluid animation for "good" animation. The thing is the animation principles are important because they visually help the action move. Maybe people don't really form into s-curves in real life, but in a quick motion you'd be amazed how natural it looks animated. Otherwise, some movements look terribly stiff.
There is an important thing Japanese animation does that I wish more American animation would do, however - and that is visuals. If Akira Kurosawa ever animated, I think he could be just as effective as he was in live-action. There are Japanese animated films that have made me hold my breath with a single frame. My favorite animated film is "The Professional: Golgo 13" because of this - every short looks planned out and detailed beforehand. I believe this to be one of the prime reasons animation is such a great art form, because it is literally art in motion. All in all, Peter Cheung was head-on when he said that both American and Japanese animation could learn from each other.
...Ahem, sorry, animation student here, I like this sort of thing.

To stay on topic...anybody ever heard of those people who like animated porn better than real life porn?
