had to be done, mine:

Battlestar Gallactica (2003 version)
Star Trek: TNG, TOS, VOY, DS9, ENT
Stargate SG-1/Atlantis
Farscape
The X-Files
Doctor Who (classic and new versions)
Sliders (first couple of seasons anyway)

Welcome back SciFiBoy!

Battlestar Galactica New Version
Ghost In the Shell: SAC 2nd Gig

those 2 by far.

Firefly
Star Trek Next Generation

are some other really good ones.

Battlestar Galactica 

Farescape

Firefly

Fringe

Stargate Atlantis

Battlestar Galactica (2003) is by far the best sci-fi show IMO and is probably my 2nd favourite show ever.

Firefly, DS9, Babylon 5 were all very good too.

Caprica and SG:Universe are both looking good so far but it's a bit early to tell exactly how they'll turn out.

Farscape>StargateSG1>>>>>SGAtlantis>Dr.Who(last few series)>>>>>>>others (don't really watch much)

A person named SciFiBoy makes this thread. Now that's surprising!

On-topic: I've just realised I've never really watched that many scfi-fi shows. I remember watching Star Trek when I was little (can't remeber which one). I remember watching some eps of Stargate SG-1 and liking it (never seen the spin-offs), but I quit watching after a while. Same thing with Babylon 5. I always wanted to watch The X-Files, but quite frankly the promos they showed on TV scared me (what can I say, I scare easily).

I'm gonna try watching some of the shows recommended here.

Battelstar Galactica (2003)

X-files (until it really started to go down hill at some point, I think it was either before or after the first movie)

Invasion

Flash Forward (apparently I am one of those few that actually enjoyed the series..)

latter days Dr. Who and Torchwood (more of a chapter by chapter thing, some chapters I really like, some not really. I thought that the Torchwood:Children of Earth mini series was not very far from real greatness)

Survivors (has it aired in the US? Though my profile says US, that's because I have a US Wii, not because I'm there...)

I thought season 1 was okay, but there are only a couple of characthers who seem to have any quality or potential, and the plots were very hit and miss tbh

Hello

My top is :

The Twilight Zone (best TV show ever imo)

FireFly

Doctor Who

Farscape

Bye.