5. Star Trek
Star Trek is, without a doubt, the most famous failure on this list. It doesn't have the relative obscurity of the other shows, but it was neglected in its time and abandoned just the same. Many casual TV viewers believe the series went on for a long run, but that was only the perception created by its rise in popularity through the following years of syndication. At the time it just barely avoided cancellation to last three seasons before the final ax.
The series was ahead of its time in both predicting the future's technological capabilities and more progressive social norms. The Enterprise's pocket-sized communicators were today's cell phones, and their main screen viewer was capable of the original Facetime. Beyond the hardware lay a series that showed a future when bias was overcome: women and men of any background treated each other as equals, and Captain Kirk and Lieutenant Uhura famously participated in TV's first inter-racial kiss.
The 1960s were a time of great change and Star Trek was still just a little too far ahead of the culture curve. That would soon change in the next decade. As the more liberal seventies came and sci-fi popularity exploded into the mainstream thanks to Star Wars, the crew of the Enterprise received the enthusiastic welcome they missed over ten years earlier. The series was revived as a successful film series and became an entertainment franchise with award-winning spin-off series.