I was a big fan of science fiction and fantasy as a child, so pardon my questionable taste in music.
My favorites:
Star Trek by Alexander Courage, My #1 of all time.
Space 1999, 1st Season by Barry Gray.
The Greatest American Hero, "Believe It or Not", by Mike Post.
Battlestar Galactica, by Stu Phillips.
Buck Rogers in the 25 Century, by Stu Phillips and Johnny Harris.
Airwolf, by Sylvester Levay.
Knight Rider, by Stu Phillips.
Streethawk, by Tangerine Dream.
Babylon 5,by Christopher Franke.
Gene Roddenberry's Andromeda, Alex Lifeson, "March of the High Guard", it's weirdly beautifully and different.
Last not least, V, by Joe Harnell, which is still haunting to this day.
For regular shows:
Baa Baa Black Sheep, by Mike Post and Pete Carpenter, having the cast read off the first line of the third verse of the Whiffenpoof Song was a nice touch.
Magnum PI, by Ian Freebairn-Smith.
Saint Elsewhere, by Dave Grusin and J. A. C. Redford.
The A Team, by Mike Post.
Hillstreet Blues, by composer Mike Post.
Miami Vice, Jan Hammer and Tim Truman, the music probably helped keep the show on the air for the last two seasons.
Documentary series:
Vietnam, The Ten Thousand Day War, Cameron Hawkins for the theme, Pete Pedersen for the series. Richard Basehart who narrated the introduction to Knight Rider, narrated this series and his narration goes along brilliantly with the music.
Dishonorable mention:
Blue Thunder, for using only snippets of Arthur B. Rubinstein's soundtrack from the film.
From the first Japanese anime that made it to the United States:
Star Blazers / Space Battleship Yamato, by Hiroshi Miyagawa.
Robotech, by Ulpio Minucci, Harmony Gold's adaption of The Super Dimension Fortress Macross.
Nobody likes the “Mission Impossible” theme? It’s timeless.
Miami Vice had some great guest artists too. My fave:
https://www.youtube.com/watch?v=Jw135y5IL7c
(short version)