Not too long ago I began a discussion with a female friend of mine about why American women are more likely to read manga (as opposed to American comics).
It couldn't be the sexuality expressed in US comics, because as bare as some of the heroines are these days (*cough* Phantom Lady *cough*), manga has naked women everywhere - not to mention girls battling evil in schoolgirl outfits. In fact many of their "superhero" costumes ARE schoolgirl outfits... with VERY short pleated skirts. So I have to believe that most girls aren't going to be discouraged from picking up a Birds of Prey because Zinda's showing too much leg, or reading Legion because Supergirl seems to have misplaced to mid-portion of her costume.
So, I asked my friend, what is it?
She actually came up with an interesting theory. She said that it was probably because girls care more about the personal lives of characters than they do the action.
The more I think about this, the more I believe she's probably hit the heart of it. We like the action of the comics, don't get me wrong, but the heroics of said super beings are meaningless if we don't care about the characters - and it's hard to care about the characters if we don't hold some interest in their personal lives.
For example, lets take Invincible. Invincible is a comic I enjoy for more than just the story or the action-packed battles. I enjoy it because I like Mark Grayson. He's a good kid trying to deal with his family falling apart, college woes, a girlfriend he's fallen in love with who's powers seem to be messed up, and many more issues that the average reader can relate to. Because of this I not only sympathize with him - I empathize. In doing so I have a vested emotional interest in what becomes of Mark. So when he's beaten within an inch of his life I worry what will become of him. So I read the next comic as well. Slowly but surely I've been hooked. Same thing with Legion - its not the epic fights to save the Universe that keep me reading, its the jokes about "Microlad" and the developement of Brainy's feelings about Dream Girl - and their engagement that I really hope is followed up on (well that and the fact that I've always had a small crush on Brainiac 5 that I can't explain). Because I care about the characters, I care about what happens to them and their world.
Girls usually need a emotional attachment to a story to keep reading. Without that empathy for the characters most of us lose interest. Manga offers that emotional outlet, it allows girls to imagine that they could be that girl with powers, or even just the girl with a wacky cast of friends dreaming about getting into Tokyo U. It's why I'm so attached to Kitty Pryde, because when I was a kid reading X-Men, I felt as if I could have been Kitty if I had been born to her world. Being drawn into a character's personal world makes you feel as if you know them, as if you could be their friend. Girls in America don't expect this connection from characters in American comics - as US comics have the stigma of being boy's action stories. I think if more girls were handed Birds of Prey or Invincible or even Elfquest to get them interested they would be just as interested in them as I am. I just had the advantage of learning to read on Wonder Women comics.
Of course this is just one reason that there are more men reading comics, and it was mostly to answer the question of why girls are more willing to head for the manga shelf.
It may be that girls are suckers for a good romance too - and manga is big on true love type romances, as opposed to US comics where the characters are always sleeping around. Also, manga is "cool", for some reason US comics are still geeky. Damn you Yu Gi Oh!