TV show: Doctor Who
Book: The Hitchhiker's Guide to the Galaxy
Movie: I honest to God can't decide there are WAAAY too many movies I can think of. Although, I guess if I had to pick the most momentous Science-Fiction movie for me it would have to be Jurassic Park. Simply because it was the first movie I ever saw in a movie theater!
*These are other books/movies/TV shows that I do have to seriously acknowledge:*
books: Watchmen, A Wrinkle in Time, The Giver
TV shows: Star Trek (Original series & Next Generation, although I did like the other shows as a kid, I just haven't seen them recently enough to be a fair judge), Firefly, Futurama, Mystery Science Theater 3000, Blake's 7, The Hitchhiker's Guide to the Galaxy, The Prisoner (The original version), and The Twilight Zone
Movies: *Takes a deep breathe* Back To The Future Trilogy (The first and second one might actually be my favorite sci-fi movies), Original Star Wars Trilogy, The first two Terminators, Alien, Aliens, Star Trek, Star Trek II, III, IV, & VI, Serenity, Watchmen, Iron Man, The Day the Earth Stood Still (Original), John Carpenter's The Thing, X-Men, X2, the Spider-Man movies, the first two Superman movies, A Clockwork Orange, The Matrix, Minority Report...I'm sure there's more but that's all I feel needs to be mentioned for now.