To my mind the best SF film ever was the David Lynch version of 'Dune'.

Yes, I know that it was universally panned at the time it came out but it's very weird, has got great visual flair and is an homage to Herbert's original book. I also feel that it's a genuine SF fan's film - not just a soap opera or thriller with great bleeding chunks of genre SF stuck on with wall-paper paste - as most TV and movie 'Sci-Fi' appears to be.

I seem to remember that, at the time it came out (mid 80s?), Harlan Ellison claimed to have been banned from from the press screenings (or whatever they're called) because the studio knew that he would LIKE it. He suggested that this was because the film took so long to make that the studio management changed part way through. The new management couldn't bear to see something made by the old management succeed - so they only invited critics who they knew would hate it and give it poor reviews.