hmm, its hard as many of these have been with me my whole life, my major sci-fi TV & Movie influences as a child apart from ST were probably -
Doctor Who which used to make me hide behind the sofa from about aged 4 (from Pertwee era, but TB was my doctor, I met him once in 1976 and once last year)
The Tomorrow People (first shown 1973 ! but I remember seeing it after school), aged about 6
Space 1999, 1975, aged 6
Star Wars since 1977, aged 8
Blakes 7, 1978, aged 9
BSG since 1978, aged 9 (btw I refuse to accept the existence of Galactica 1980)
Hitchhikers Guide to the Galaxy 1981, aged 12
Books (other than the adaptations by James Blish whcih I used to get out on my mum & dads library cards) included all the Doctor Who books, kids books by Douglas Hill (Last Legionary), Patrick Moore (Scott Saunders), Asimov (Foundation & his short stories), Frank Herbert (Dune), EE Doc Smith (Lensman).
Other written sci-fi influences were comics - The galaxy's greatest comic 2000AD, the short lived Starlord (home of Strontium Dog & Ro-Busters until it merged with Thargs mag) & some v.old copies of Look & Learn that were given to me (The Trigan Empire, Jason January Space Cadet)
As an adult the ones that have really been amazing have been
B5 (The Empire at War mod for this is brilliant btw)
Firefly (killed before its time)
BSG (and now Caprica which is also v.good)
As for me, it's hard to pick a single favorite.. It really depends on the media format...
In Print... the Honor Harrington universe.. hands down..
in Television.. Babylon 5...
In console games I am extremely fond of the lore behind Dead Space..
In PC gaming, I would have to go with.. Sins of a Solar Empire..
As for film... the Alien universe.. (up to Alien 3, everything after was crap)
And as a random bonus title.. I also rather like Childhood's End by Arthur C Clarke
To be honest, there isn't much Sci Fi that I don't like... though I prefer the creepy and existential stuff over "rebellion against a certain evil empire" type.. not that those types are bad... I just find myself rooting for the evil empire more often than not.. heh..
Just wait until the Romulans are playable in STO.... I will subjegate you all and crown myself empress... mwahaha...
In terms of hours devoted to watching probaly Bablyon 5. The main story is something I just have to keep coming back to. Also there are a lot of Trek crossover actors who make it very special to me. Notably Andreas Katsulas, may he rest in peace. J'Kar and Londo make for one of the most entertaining relationships in Sci-Fi. Wish Andreas was still with us, he made an awesome Romulan as well.
After that it would most likely be Stargate. Can't get enough of RDA. He just makes me laugh. Its great because its a much lighter take on scifi, for the most part. A lot of humour and the fact that Jack stops Carter everytime she goes in to technobabble mode is awesome winness.
Not sure if it counts but I recently spent a lot of time going through Gundam 00 a few times. Surprisingly well written and incredibly enjoyable even though i'm not really an Anime person. I get the feeling I would be if I spent some time finding stuff to like though.