I certainly have written enough words at this point about bad super-hero costumes, but I wanted to take advantage of the tidings of joy in the air at this time of year to point you to a site that features nothing but great design -- Project Rooftop. From their "About" section:
Project Rooftop is where cartoonists and illustrators bring their costume design skills to task in tribute to the superheroes and villains we’ve grown up with. This site is intended to promote excellence in costume design as well as foster continued interest for these amazing characters.
All characters are copyrights and trademarks of the respective publishers and creators. All of the designs here were created not for profit and this site is used solely for artistic enjoyment.
Whenever you feel the urge to see what other really creative, talented people can do with super-heroes, I urge you to browse through the Rooftop archives. They're really something special.