There's the whole stereotype of women not liking comics because of the costumes. And by that I mean the fact that women in comics tend to wear costumes that are deemed 'revealing' or 'overly sexual'. It's that kind of thing that makes me shake my head in shame for the rest of my gender. Sadly, people actually believe the aforementioned points to be, gasp, relevant. Could be just me, but it seems like calling water wet. 
Spandex bodysuits, sexual/revealing? No, really? 
But what irritates me the most is that people who complain about women's costumes being too sexualized neglect to examine the costumes of the male heroes. The Thing runs around in BOXERS. Nothing but boxers! And you say Phoenix's costume is sleazy and inappropriate?
If someone were to complain about the costumes of, say, Selene (as the Black Queen, not so much in Necrosha...), then their point would be less idiotic. But only slightly. The Hellfire club is, after all, an organization that pretty much exists for indulgence, ergo saying that the outfits the women wear are skanky is incredibly stupid. They're SUPPOSED to be sleazy. 
Another thing is that people who complain about the revealing nature of the typical spandex costume fail to take into account that it's goddamn spandex. The stuff is MEANT to be extremely fitting. Why spandex, though? Ease of movement, not to mention cutting down on noise, wind resistance, and other possible encumberances. It's for the same basic reason an olympic swimmer shaves their head. 
Lastly, what right does anyone have to tell someone else what they should and should not wear? I mean, you may not like the way something looks, but what makes you think you can dictate some set of rules as to clothing? If a comic book character (who is, by the way, FICTIONAL) can't wear something that is pretty damn practical, then heaven forbid one should go out in public and see the abominations people wear on a day-to-day basis. 
 
As a side note, some costumes should not be worn. I'm not saying that they can't be worn, but it's not advisable. Case and point, the horror that Kitty came up with shortly after joining the x-men. Holy random amalgam of colours, Batman!

Here's what I'm talking about: using a relatively random system (closing my eyes and clicking my mouse on a web page of superheroes), I chose a female hero and a male hero.
 
Female Hero: Spider-Woman
Male Hero: Ronin
 
Now, let's see what their current profile picture is here on CV.
 
Spider-Woman:

well the thing is, they do show the male body alot in marvel, they just have anything that hugs the junk, thankfully i never want to know how big hulks package is,
 
Now when yhou look at women, they have BOOBs some times they have BIG boobs as my ex had big boobs, it can be hard to dress those things without showing them off, and you do not have to try, also women love to flaunt it,  and hate when guys they dont want, want them, so transfer that over, it would harder for a sleazebag to fight black cat, cause her rack is distracting

What I find weird is how Superheroines somehow find costumes that go underneath their boobs and wrap around them. Also how their costumes go into their butt cracks and wraps around it as well. 
 
IFanboy had a good article on this subject:
http://www.ifanboy.com/content/articles/High_Heels_and_Cleavage_Windows__Why_Can_t_Female_Superhero_Costumes_Be_Sexy_AND_Functional_

@Squares

Can I recommend something some light reading to you?

http://www.comicvine.com/myvine/darkmount1/the-sorry-state-of-the-superhero-comic-book-today/87-75259/

@Darkmount1: No, actually, you may not. That's what PMs are for.

Classy as hell.

I dont know. Considering the slutty nature of modern clothing, if female superheros did exist, I really dont think they'd be much different. I drove past my old high school yesterday. At most, 25 girls, all wearing tight jeans, shirts with cleavage, or bra straps visable. I only got a quick look, cause you know driving, & also I didnt want anyone to think I was a perv. Also, female supers would be posing in magizines like Maxim, FHM, maybe even playboys.

Yes, comics exagerate, but not by much.

@COBRAMORPH: Hm, fair point. I remember an issue of X-Factor featured M posing naked for a magazine cover (Vogue, maybe?), but one should also consider the fact that M also happens to be an heiress, and they're fairly well known for doing nude photoshoots...

You have a fair point- many perfectly ordinary people walk around practically nude in everyday situations, so why wouldn't superheroes?