I've always thought of science fiction as a literary medium. Throughout the entire 1970s and 1980s I didn't own a television and only saw any programmes on occasions when visiting friends who liked TV. I had a very low opinion of adaptations of scifi to the screen. Some of my friends might've bothered with the sillyness of 'Blake's Seven' and whatnot but I stayed with books as a primary source of entertainment. I became aware, however, at the end of the 1980s of the existence of some better quality programmes and TV began to interest me for the first time since childhood.
In 1992, at the age of 39, I got my first TV set in order to watch Star Trek TNG (among other things). Over the years since then I've certainly seen some utter rubbish on the small screen but there have also been some very good scifi adapations. Here's my list of the shows worth bothering with.
These may be the 11 finest examples of Science Fiction being adapted for the medium of television. I'm not sure because I haven't seen every Sci-Fi TV show ever made (thank goodness!).
In some attempt at a vague order of excellence, starting at the top:
1) Zipang (Tokyo Broadcasting System - Japan) best science fiction I've ever seen on TV.
2) The Dollhouse (Fox Network - USA).
3) Flashforward. (ABC TV - USA).
4) Dark Angel (Fox Network - USA).
5) Invasion: Earth (BBC TV - UK).
6) Ultraviolet (Channel Four - UK).
7) Battlestar Galactica (the remake) (Universal/Sci-Fi Channel - USA).
8) Star Trek (mostly TNG, DS9 and ST:Enterprise are excellent - Voyager and TOS not so much) (Paramount/UPN - USA).
9) Firefly (Fox Network - USA).
10) Out of the Unknown (BBC TV - 1960s to early 70s - UK).
11) The Outer Limits (ABC TV - USA) (+ Sci-Fi Channel revival version).
P.S: Of course there's Dennis Potter's 'Karaoke' and 'Cold Lazarus' but they belong in a special category of excellence by theirselves.