So while there are genres that include regular humans, such as the ones you listed, I would contend that the number of genres that include a main cast that are above and beyond regular humans relative to their world is greater. Additionally, I would say that most sci-fi actually do contain humans that are "plain jane humans with no special powers". Now, keep in mind that everything is going to be relative to the world they're from. But for example, I couldn't really call most main characters from something like Star Trek "plain jane humans with no special powers". The show tends to focus on the best of the best, with the most average of all being, weirdly enough, the captain. But even then? I can't really call Picard, Janeway, Kirk, or Sisco average.
Though I guess Star Trek does have a way to writing their characters in such a way to seem pretty average despite being well beyond the average character for the universe.