In addition to Trek-verse science-fiction I've enjoyed
StarWars,
Red Dwarf,
Alien Nation,
Babylon5 and
Firefly.
Babylon 5 is at the top of my favorite sci-fi list. Yes it was under budget, but financing aside, the writing was A+ and consistent. And speaking of budget... tell me those early TNG episodes do not make you cringe when you watch them now!
Sliders was another series I enjoyed in high school. It wasn't a necessarily thought provoking show, but it was fun and amusing.
I really liked the first two seasons of the
Battlestar Galactica reboot, though my interest began to wane when it didn't synch with my schedule.
I also liked
Threshold, not so much the concept, but the dynamics of the characters. Peter Dinklage and Brent Spiner's respective characters playing off each other was always fun to watch. And Carla Gugino was, and still is, HOT. I thought it was a well casted series, even though he that shall not be mentioned was involved in the project.
Another in that realm of Aliens Among Us that I thought was an excellent show was
Invasion. The intrigue was palpable and compelling.
I never cared for
X-Files, I thought Mulder was a mopey prat and I never understood what Scully ever saw in him.
SG-1 was another one I couldn't get into. I found the characters arrogant and unsympathetic and always rooted for the 'bad guys', although the
SG-1 characters weren't nearly as unlikable as the
Atlantis crew. I'm all for the Wraith invasion there.
Heroes is a current favorite of mine, although I've been a little bothered by the directions of things this season and the allocation of powers and characterization of the female complement of the series.
As for the more supernatural/horror type of series, I liked
BtVS before it became pedophile fare with the introduction of Angel and
Wolf Lake. I thought it was a smart and cheeky series, and
American Gothic. Gary Cole's character was CREEPY TWISTED

. The Sci-Fi channel needs to re-run that again!