That part I don't agree with. That's like saying all American comics are about superheroes or that all 90s comic books look terrible: that may be the majority but that doesn't define it.
Wait...*click* *click* *click*
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Okay, according to Wikipedia it turns out that what you mentioned does more or less define manga. Oops.
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So, wait, what does that make Lupin III? Anyway there are still plenty of Japanese comics that are good, you just have to try a lot harder to find them. If you only like hero comics, though, I can name several.