Star Wars, by far, is my favorite film franchise - all 6 movies. The originals are classics, and while not as good, I honestly think the prequels do hold up on their own too.
I also love the Jurassic Park trilogy (especially the first 2 movies), and the Back to the Future trilogy.
Probably my favorite sci-fi/comedy show is Red Dwarf. Love that show!
The only Star Trek series I ever got into was Enterprise. I would watch The Next Generation here and there, but really never got into it.
Reading the post above me, I can't believe I forgot to say the Fifth Element. I love that movie! Also I really liked the Island (Ewan McGregor and Scarlett Johannson).
Outer Limits (TOS)
Twilight Zone
Star Trek (TOS)
Voyage to the Bottom of the Sea
Firefly
Space 1999
UFO
Buck Rogers (1930's through 1950's)
Time Tunnel
All time Film Classics (in no particular order):
Alien
Star Wars
2001 A space Odyssey
When Worlds Collide
War of the Worlds (1953)
Day the Earth Stood Still (1951)
Day of the Triffids (1962)
It! The Terror from Beyond Space
The Thing form Another World (1951 and 1982 versions)
Crack in the World
20 Million Miles to Earth
5 Million Years to Earth
First Spaceship on Venus
Island of Terror
Destination Moon (And that is just the fraction of my collection that I can recall at the moment)
All time favorite: ST Voyager. After that, any ST except DS9, BSG (both 1978 and 2004) Space 1999, Lost in Space (series and movie), Seaquest. All the SW movies are watchable, but my favorite is Empire Strikes Back.
Raymond Burr was the Original Godzilla!!sign1 , sorry, couldn't resist that. I too am a fan of the original Godzilla and being about 6 years old when I first saw it, it scared the heck out of me!
Star trek TOS - then all the rest.
Battlestar Galactica TOS - the new one?, not so much.
FIREFLY, yes, in capitals!!!
Metropolis - Fritz Lang rules!!!
Serenity
Star Trek 2009 - despite the starship interiors. They just sucked.
Pretty much anything Sci-Fi, with a few exceptions.
Raymond Burr wasn't really in the original Godzilla.
His scenes were filmed and added by the American distributor for the American release. So, an editors cut wouldn't include his scenes because he's not supposed to be there.
I am actually in the total minority group of people who have never seen star wars or star trek, it amazes some people. I suppose I should really watch them, but there are now so many I wouldn't know where to start. I am however a huge doctor who fan!
Star Wars comes as my favourite science fiction movie because it is the only one of the franchises where I generally like everything about it, or can find good in almost all of it.