Every once in a while a show startles its audience like Marty McFly rocking 1955 with Johnny B. Goode in Back To the Future.
These shows bring a twist so innovative that the majority of television viewers just aren't quite sure what to make of it at the time. Small packs of devoted fans keep the show alive, with repeated viewings that launch discussions analyzing the smallest details of their beloved stories. It is only later on that these neglected concepts are vindicated by either successful future re-launches or series that, while technically unrelated, carry on the spirit of these pioneering shows.
These five series all featured innovations that were not appreciated in their own time. Only years later do fans reflect on "Why wasn't that a hit?" because the concepts in these shows seem to be typically successful elements of a hit show. Perhaps in a different day and age they would have had many more seasons of stories added to their legacy. However, in their own era, they were too far into the future.