Some o' my favorite marvel costumes:

Moon Knight-Just plain awesome.
Spider-Man-the red and blue AND the black costume are pretty bitchin.
Sunfire-One of my absolute faves!
Nova-I love the "bullet-head" helmet!
Hawkeye-mainly for the late 70's early 80's era.
Ghost Rider-The Dan Ketch version is pure Bad-ASS!

Scarlet Witch-Wanda is hot no matter which costume she's wearin'
Black Widow-Natasha's basic black jumpsuit is sweeeeeeeeeeeeet!
Dave Cockrum's Phoenix and Storm designs are the best either of them ever had.
Aurora-She was so fine in the yellow,black and white uniform she had for awhile.