As much as I see these movies as filled with bad acting, cliche story lines and predictable endings, I believe the breadth of "view" of a new universe in Star Wars is worth remembering. I remember very clearly when it came out, and it left audiences everywhere STUNNED. No one before this had attempted to create a whole universe, a whole alternate reality as in the vision of Star Wars. Looking back over 30 years, it's easy to forget this.
My appreciation for some SF movies revolves around the books they're based on. For that reason I'd have to say 2001 is up there. The new War of the Worlds is up there, though I am sure there will be many who disagree.
AI was a tremendous concept. I believe most people will reject it because of where it leads. That's not Spielberg's fault. He just held the mirror up to the pop-culture of today and showed where it ends.
I can't believe no one has mentioned Minority Report.
[edited to add:]The Matrix is so full of itself as a self-conscious effort to be "concept-driven" that it's absolutely laughable. Just think, that whole super-advanced Sim world was just too dumb to implement Norton AntiVirus before Neo showed-up. Or even ID them when they "materialized." What a crock. I didn't wast my time with 2 & 3.
Forbidden Planet and Robinson Crusoe on Mars. are classics.