The word "flop" gets used around here way too easily. What is a Flop. The only show you listed that I would call a "flop" is Firefly and that was mismanaged from the beginning by Fox. Star Trek was never a flop, and neither were the Stargates (3 series) and Star Trek (almost 20 years of being on tv continuously).
I don't mind fantasy, but man do I miss the space based TV show. My favorite TV shows ever are in that genre (Farscape, TNG, Babylon 5) and to not have one since BSG is a shame.