I know, I know. But I'm biased :D
edit: I'm open to suggestions about other scifi shows, so fire away
The only 2 Sci Fi shows that are worth watching - BSG & Firefly
I've never really taken in any sci-fi shows, but I hinted at the one I've watched pretty much every episode of: the collossal Quantum Leap!
Man, I remember watching some random Quantum Leap episodes on TV as a kid, but the only thing I recall is that I kinda liked it. Babylon 5 was cool as well.
Quantum Leap was the most awesome example of awesomenessnessness of all time. And the final episode was amazing (awesome).