How inherently sexist is the superhero genre? It's so inherently sexist that pictures of superheroines fully clothed - ie, dressed like many male superheroes are dressed, in outfits that don't reveal 80% of their flesh - feel newsworthy.
Artist Michael Lee Lunsford took on a redesign project, putting female heroes in costumes that weren't simply painted on. His statement:
An exercise in character design, attempting to clothe the heroines nearly all the way and not making them painted-on, while still keeping the look of their original costumes in some way. Hopefully keeping them looking as iconic as the originally were. Just showing what can be done with a costume breaking outside the barrier of the norm.
NOT the point of this: some moral code I’m trying to push on you
But it's hard to miss an obvious moral point here: these characters still work when clothed. Power Girl is still Power Girl without the boob window. Zatanna still works without the burlesque outfit. I think Lundsford errs on the side of baggy pants in some of his designs, but that's about the only critique I would have.
And for those invariably about to weigh in with 'Male superhero outfits are tight too!,' think on this: how many male superheroes are showing skin? Hawkman, Namor... those are the two biggies I can think of. They're usually covered head to toe, and it's not unusual for male heroes these days to have pants and coats, not just spandex. Female superheroes are, almost always, showing a ton of skin in addition to having ultra-tight outfits.