If they can make Thor and Captain America's costume look cool then they could have easily made Hawkeyes look cool. Just sayin'.
Except Cap's costume looked dumb. In the comics, characters are drawn with much larger shoulders, smaller heads, and taller proportions than real people, even perfectly fit people like Chris Evans or Jeremy Renner. In the movie, Cap's head looked to big and his eyes looked to close together. In the comics, they can manipulate everything to make it look "right" even though it's not really realistic.