Hi, My name is George and I'm a Sci-Fi fanatic...
After some serious culling I'm down to about 50' of SF novels in my library. I stick mostly to Hard SF but still read pretty much everything from Poul Anderson to Roger Zelazny. My SF film/TV collection isn't nearly as extensive but still pretty good sized and I have a fair amount of stuff on VHS, LD, and DVD.
As far as ST is concerned I'm definitely in the original series and TNG (after the first season or two) camp, could never really get into DS9 although I tried, liked some and hated some of Voyager, and was equally mixed on Enterprise. Outer Limits was consistantly great and Twilight Zone almost as good. Tried to watch Babylon 5 but just couldn't. If pressed I will admit to watching the original Battlestar Galactica, Buck Rogers in the 25th Century (the annoying robot's name was Twiggy), My Favorite Martian, Lost in Space and most everything else that's been mentioned so far. I really enjoyed the first few seasons of Farscape but they lost me towards the end, I'm a big fan of SG-1 (even the new season). There is one series that nobody else has mentioned so far that I really liked and that is Firefly. Fox did everything they could to make sure it failed, and sure enough it did. If you didn't catch it when it was on originally I would highly recommend you catch it on Sci-Fi channel while they are running it now (Friday nights before SG-1 and Atlantis) or just go buy the DVDs.
On the movie side of things I'll go along with most of what's been said so far and add a few more. I'm a big fan of Ray Harryhausen's work and think that Fist Men in the Moon, Mysterious Island, Earth vs. the Fling Saucers, It Came from Beneath the Sea, The Beast from 20,00 Fathoms, and 20 Million Miles to Earth are all at least worth a rental if not a permanent place in your collection. Other old fav's include The Time Machine, When Worlds Collide, Them, Day of the Triffids, 5 Million Years to Earth, The Crawling Eye, and The Blob. More recent stuff would include Soylent Green, Contact, Frequency, Dark City, Forever Young, and The Fifth Element. I'll also admit to liking The Postman and don't think it deserves the bad rep it has, even if it wasn't nearly as good as the book (but what movie is?), Waterworld still sucks though.
Things I'd like to see: Foundation of course(although it would have to be a lengthy mini-series to even begin to do it justice), Card's Ender Wiggins trilogy (same), Robinson's Red/Green/Blue Mars trilogy (same), Pohl's Gateway trilogy (same), Niven's Ringworld (at least the first one), Stephenson's Cryptonomicon, and, and, and...