Saw Flash Gordon at the cinema when i was very young. Still really enjoy it now. Ming is one of the my fave bad guys of all time. That film has a great cast. Can't beat a bit of Brian Blessed
Tron is another one i cant get enough of (could be the best disney film ever made). i hope the new film is up to scratch, the preview that's been released looks great but you never know how the film is going to be, trailers can be very deceiving (just look at the phantom menace?!)
Dune and Blade Runner are obvious classics but i still think the 70's had some of the best sci-fi in my opinion. You guys have already mentioned a few i don't know though so Iv'e got some researching to do now!
oh and megaforce rules!