I just want to say, this is a stupid argument. Manga and American comics are, get this, comic books. Same as European comic books. Their all sequential story telling. So what's with all the negativity. Now, I have only heard bits and pieces of Manga fans reaction to American comics but have heard much anger amongst comic book fans over manga. Being an anime fan that sort of effects me as a lot of anime are true translations of the source material. So I'm going talk a bit about how American comic fans need to shut the hell up.
First off, there's the complaint that all manga looks the same. Hm...
There are similarities. That goes with out a doubt. But most manga artists are different. Some add more "lines" to their character detail, others don't. Some focus on a more slender look, others more rounded. I mean, take a step back and look at American comics. Do you think a non comic fan is going to really know the difference between Jim Lee, Marc Silvestri, and Rob Leifeld? No. The people who do are fans of the work. Or artists who can tell the differences. A lots of superhero comics have similarities. And the artists outside outside these styles usually are inspired by artists not just homegrown but European and Asian. This entire complaint American comic fans, especially fans of superheroes, have is one that others can apply tot he medium/genre they love.
Now, outside this simple complaint there hasn't been too many real solid explanations as to why their so much dislike for manga/anime amongst American comic fans. Well, its perverted but since most American comics have all their women looking like models and sporting skimpy get ups that's hypocritical. maybe manga takes it further but Kevin Eastmen, an American creator by the way, once said that once artists get good they like to draw naked women. I have heard comic fans talk about how they've tried it and don't like it. Understandable. I don't however agree with the notion that it's all bad because you saw Akira and hated it so now you think all anime is crap. But I have this notion that a lot of the dislike for manga/anime comes form its own success. This is rather foolish because you have to understand-this success is a long time coming. And besides, there are a lot of things manga has done right that American comics could learn from but won't. Let's talk about why manga and anime is so popular right now.
1-Creator control. All manga is creator owned. They start it, they end it, bam! Finite series. We have those here in the states too but the market is primarily superheroes. So most non-American comic fans probably won't know what to try. Where as with manga if we see an anime on TV we have an idea of where to start. Plus the readiness of it in bookstores.
2-Diversity in genres vs. a majority superhero comics. Manga provides so many different styles of stories and that appeals to readers. Superheroes don't appeal to everyone. If we pushed more diverse titles to the forefront I'm sure american comics would be as mainstream but we don't. we made superheroes mainstream and its hard for those to get new readers.
3-Manga appeals to women and kids. Now superhero comics could but seemingly don't. We treat a lot of the female characters with less respect then we do the male characters. Plus younger audiences won't be too interested in having to back track the continuity for a Spider-Man or Superman.
4-Translations of material. You love Batman Begins, go to the comic shop and you got tons of Bat comics. All with heaps of continuity and sometimes different characterizations. Like Yuyu Hakusho, there's on manga and it'll stay more or less true to the TV series you saw.
Also keep in mind how manga fans and anime fans seem to be able to get clubs started in schools and have a general connection. I new barely anyone in high school who read comics but knew a ton of people who watched anime. It's just easier to "pass it along" because that's primarily how anime and manga built its audience. My uncle use to talk about how you'd find the one guy at the comic con in the far corner selling bootlegs of anime. Compound this with the fact its been on TV in some form or another for years. Plus companies like Dark Horse and Viz willing to appeal to at one time a niche market by delivering some product int he comic shops which probably appealed to comic fans who may have been burnt out on American comics or had heard buzz about the book or just generally more curious to foreign works. It slowly crept into the American mainstream and because of the diversity in the medium was able to grab fans of different tastes. DBZ grabbed these fans, Evangellion(which I hate btw) grabbed these fans, and Tench grabbed these fans.
These hatred a lot of American comic fans seem to have towards anime and manga I believe has more to do with its success then its content. They write it off as "perverted" or "looks all the same" but are really just refusing to give it a valid try. You don' like it, fine. But all anime and manga bad? Bullshit.