To avoid posting in some of the more retarded, tired threads, I'll give my input. This can't quite be as controversial as parent rights, and has much more value than whether or not Jewish tacos are the more sensible answer.
A lot of manga and anime is just plain pulp fiction. It's done in bulk, under piss-poor budgets by overworked and uncaring animation drones. There have been very few anime other than novella types (1-3 episodes) which I really liked. Some good examples of stuff that appeals to me are: Jin-roh, Armitage, Metropolis, Perfect Blue, most the Ghibli movies to name a few. Stuff that I think is crap, and a waste of time: Love Hina, Dragonball, Gundam Anything, Ranma, almost anything that gains popularity stateside. There are some that are kind of in the middle, too long to care about the characters all that much, logic too circular, plot incomplete, such as Evangelion, Trigun, Cowoby Bebop, Ghost in the Shell, etc. These are meant to be watched weekly, and have just about as much art in them as the Simpsons do...they are meant to be a simple story-telling medium, and the chopping into segments limits what can be done, so the serial nature of the story is very visible.
Another issue I have with anime is that it often fails to properly capture the plot of the manga....the comics are generally much more in depth and the cinema version does a limited job at capturing it all. Akira turned out OK, but because of the compression, it ended very abruptly, and the plot didn't make a lot of sense. Lots of fun music, bike-riding, and a growing mass of flesh...but in the end, it didn't seem to matter all that much. The manga form has been virtually unchanged for about a century, with very few combinations of art forms...I wish that some of the more artistic manga producers would have a shot at directing their own films, but that is not very common. Manga artists have a few failings in relation to Western comic forms, the biggest one is that they never specialize. One guy does almost all the work, including writing, art, pencilling, editing, and production aspects. Not to mention that they are on tighter deadlines, and produce more output with each comics. It's somewhat hard to concentrate on refining your work when you have publishers breathing down your throat for the next 20 pages each week, so that they can put it into Shonen Jump. Like I said, its pulp fiction, and has all the failings that pulp fiction does.
I agree that the medium is better for certain things, but I'd be hard-pressed to say that most Japanese comics and cartoons had higher production values or greater artistic content than Western comics/feature length cartoons. Disney is a well-oiled machine, and has slaughtered more fairy tales than I care to think on, but they have consistently shown innovation and aesthetic in the cartoons they make...they are very rarely the same visually, and usually look very nice despite a horrible plot.