Depends on the character and the costume, really. I've never had much of an issue with leotard costumes, but when you add in shit like thongs and boob windows it just seems kinda sleazy and trashy.
Quantity also has a quality of its own. If a few female characters are wearing skimpy outfits its alright, but if every female character is, it's distracting and (again) trashy.
At the same time, some characters just work better without pants, like Wonder Woman or Bleez.