I like anything sci-fi, preferably in deep space, and as long as it's somewhat serious, not a comedy. I don't find much entertainment in comedy.
These days however there isn't anything new to watch so I'm stuck in an endless loop with Star Trek, Battlestar Galactica, Babylon 5, etc.
So I don't watch TV often these days. I can only hope something new, great space sci-fi, gets made, and supported.
But, with that said, I don't exclusively watch space sci-fi. I do watch a few other genres, and some docu when I have time for it.
Game of Thrones, Vikings, and Da Vinci's Demons.
Arrow, Continuum, Almost Human, Falling Skies, Under the Dome, Defiance.
Horizon, The Universe, Through the Wormhole, Ancient Aliens.
There's a lot of old shows that I've seen. Most of them have been listed in the thread already. :-)