Terminator: The Sarah Connor Chronicles. It lasted two seasons, and at the end of season two, I was very excited to see what came next. Little did I know, nothing would come next, because it just so happened to air on the wrong network. Fox killed it.

I also liked Firefly. It was a very good science fiction show, but unfortunately, it aired on the wrong network, and only lasted one season. Fox killed it. Fortunately, though, the show launched one of the greatest science fiction movies ever made; Serenity, so at least something good came out of it's cancellation.