Here's my list of SF shows, in order of greatness of being SF shows. A longer show of the same average goodness ranks higher than a shorter one.
b5 >bsg >firefly >farscape >ultraviolet >SG1 >DS9 >TNG >Odyssey 5 >Crusade >Dollhouse >Caprica >SGU >Dr Who >Blake's 7 >TOS >Futurama >Misfits >QL >Dark Skies >TAS >V >VR5 >Roswell >Outer limits >X Files >S:AAB >SGA >Quatermass >WotWorlds >LEXX >Flashforward >Sliders >Torchwood >seaQuest >Threshold >Alien Nation >BSG:1978 >Prey >Planet of the Apes >Time Trax >Earth 2 >E:FC >Buck Rogers >Space 1999 >Andromeda >Voyager >UFO >BSG:1980 >>>>>>>> Enterprise