Classic (and some not-so-much) sci-fi TV shows from the 1950s through right now. With the exception of "Futurama", I've elected not to list any animated or anime shows – that would be another list on its own! ("Futurama" is here because 1. It deals with some real science fictional elements, and 2. It's my list, so there.
Hopes this brings back some fond memories for you!