Despite Jeb Bush’s commentary, there is more to “Supergirl” than the fact that Melissa Benoist is “pretty hot.” “Supergirl,” CBS’s newest Monday night attempt to capture a young adult audience, is far from super. But the mere fact that it has a female lead, in a genre where they are about as common as quality Nicholas Cage movies, makes it culturally significant. We spent much of our childhoods watching cartoons like “Superman: The Animated Series,” “X-men: Evolution,” and “Batman: The Animated Series,” as well as movies like Christopher Reeve’s Superman (and unfortunately all of its sequels). Later on we enjoyed Christopher Nolan’s Batman trilogy and even watched a bit of “Smallville,” before it turned into a soap opera. Yet throughout our superhero-filled childhoods we personally never once saw a superhero movie or TV show with a female protagonist. Why?