Star Trek
LOST
Fringe (need to watch season 2)
Battlestar Galactica (need to finish season 1)
Heroes (seasons 1 and 2 only)
Sanctuary is an interesting show as well. I missed an episode of FlashForward and need to catch it on DVD. I've heard good things about the Stargates also.
EDIT: @Machina: You're probably the only person I've seen that thinks DS9 and Voyager are better shows than TNG.