Kids aren't going to compare and contrast storytelling techniques. They are going to get the one with the most tits and/or blood in it.
IDK, man, when I was fourteen I was able to realize that Chobits was complete shit. The guys were too, despite the naked Chii that Hideki manhandles ten pages into volume one. In any case, that's what kids will do with actual books, anyway, so I don't think there's any way to stop that. People will always read what's more interesting to them.
I was talking about consistency in character development. I'd expect a little quality out of my characters even in mainstream comics, and I think collectors would feel about the same. Then again, they get different writers all the time, so I suppose that's unavoidable.
As for manga being renowned for lack of character development... I feel that's pretty much the opposite. I feel a lot more of a connection with particular characters in many of them. I feel like you're still talking about Naruto and Bleach, which I'm not, because I've already discarded most of the mainstream stuff (both American and Japanese) in the discussion. In regards to your pacing argument: if everything is kept short and to the point, why is Naruto more than forty volumes long? I actually think English-language comics are more short and to the point, and that's what I think Japanese comics should adapt.
One could go both ways with the movie argument. I read a book for a creative writing class last semester, in which the author (a professional writer herself) claimed that cbooks are essentially useless because movies have the propensity to affect the reader more with its visuals. Obviously, this is kind of dumb (especially considering the numerous movie adaptions of books that have failed), but it might have some truth to it in the attention spans of the youth might be kind of lacking. Comics (manga and graphic novels) portray a story with visuals, which can hold their attention. If that comic has a cinematic feel to it, it might grasp their attention even longer.
As for the comparison of actual authors, I can't argue anything about that. I know people who love the Grapes of Wrath
and Twilight and turn out to be stellar writers. One of them goes to school for (ironically) Comparative Literature, right now.
Again, I'm not like, "oh the library should obviously only include x", because that's dumb. Just include the best of both. It's not that hard, because some from each category are obviously better than others.