-1. If we are talking about a down to earth movie I would say looks aren't important but i'm one of those "conditioned" people who expects a good looking chick for the Superhero whether or not said Superhero is shallow. He deserves hotness to match his coolness.
Hot's subjective. Witness folks complaining abut Margot Kidder, Maggie Gyllenhaal, Scarlett Johansson, Anne Hathaway...well just about any actress cast in a superhero movie.