Doctor Who - the longest running sci fi show in the world
Toorchwood series 1,2 ,3 series 4 is rubbish
The X Files
Buffy The Vampire Slayer
Star Trek Origional series
Star Trek: Deep Space Nine
Star Trek: The Next Generation
Stargate sg1 ,
Stargate Atlantist
Stargate Sgu not as good as the others but it finishes off the stargate series
Charmed
Fringe
LOST
Sliders
Lois & Clark: The New Adventures of Superman
Buck Rogers in the 25th Century
ALF/Thunderbirds
The Wild, Wild West
The Six Million Dollar Man
Jericho
Dollhouse
V (1983) or remake
Roswell
Eureka
Flash Gordon (1950s)