I'm doing it like
jackwabbit and name only the series of which I have seen every single episode. With some that means taping and watching it every day instead of once a week, because it already was on re-run.
Baywatch (not sure if "fast forwarding through the music clips" counts as watching them all, but I really stuck with it till the end when the swimsuits went from red to yellow and the stories went shallower and shallower. Don't ask why, though)
Boston Legal
Desperate Housewives
Eureka
Knight Rider (the original)
Lois & Clark: The New Adventures of Superman
Lost
MacGyver
North and South
Party of Five
Prison Break - wait, scratch that, I stopped in the middle of season 4
Pushing Daisies
Queer as Folk (US)
Six Feet Under
Stargate Atlantis
Stargate SG-1
Torchwood
X-Files