With the source material, at least for me as compared to western stuff like X-men, Superman, etc, is that one, it crosses all genres and appeals to all genders. Comic books for much of their existence were largely geared to a specific, very male audience, and it was made quite clear by their writing and the actions of people into comics at the time that other genders (and, to a certain extent, skin colors) need not apply to join the club.
Since I’m a girl, when I was a kid I got teased a lot for liking ‘guy stuff’ like Batman and GI Joe. The problem was, well, I liked action stuff for one, but back then there just wasn’t anything for girls. Hell, I remember them even taking Wonder Woman’s power away, because apparently women empowerment reasons?
Those comics were all written by largely out-of-touch white guys who had, shall we say, definite opinions of what a woman could look like and should act like. And as a woman, I was never impressed. Especially by the time I got to the hundredth drawing of a woman’s ass and legs framing a supposedly ‘serious’ scene.
Then I found manga, with all-women writing teams, and artists who wrote well-rounded characters of all genders and orientations (Sailor Moon had many adorable scenes between a lesbian couple, just to name one example). They drew women who were people. They were sweet, they were brash, they were rude and crass, they were funny. And who weren’t afraid to fireball their way out of trouble. Hell, they drew varied guys who were weak, strong, silly, spacey… they felt real, in a way that I’d never seen in western comics.
Another thing is that mangaka tell the story, their characters get a satisfying actual ending, and then the artist moves on to another story. None of this ‘Oh, the X-men found happiness and solved their problems! In our next comic, watch as everything goes back to the shitty status quo because we have no idea how to write different stories!’ or ‘Welcome to the 2,171st reboot of Superman, now with Extra Edge^TM (because we hear that’s all the rage with kids these days). And remember that this iteration specifically references that one part of reboot #1,023, so read that too (if you can find it lol).’
And the third thing for me is it was quite a bit more beautiful and fluid and varied than western animation. Especially in the case of the days of Too-Many-Pockets Rob and his wooden doll faces, or the small beady eyes of, well, every comic character ever. Anime and manga faces were much more expressive, the worlds more varied and creative, and they weren’t afraid to draw regular people as protagonists, without muscles bulky enough to make you think you were looking at a Macy’s parade balloon.