Based on being essential, meaning standard bearers of the genre

Empire Strikes Back
Akira
Aliens
Total Recall (original)
E.T.
Children of Men
Eternal Sunshine of the Spotless Mind
The Truman Show
Wall E
Blade Runner
Silent Running
The Matrix (first installment only)
Back to the Future
Mad Max: The Road Warrior
2001: A Space Odyssey
Fantastic Voyage
Minority Report
Close Encounters of the Third Kind
Clockwork Orange
Robocop

Honorable Mentions:
Jurassic Park, original War of the Worlds, Dark Star, Battle Beyond the Stars, Gravity & Dune.

(I'm still undecided on the new, edgier stuff like Moon, Primer and Ex Machina. Enjoyed them, but not ready to put them in a pantheon)
______________________________________________________________________________

cscpov.blogspot.com

"There's a fine line between persistence and foolishness..."
-unknown

"To Each His Reach"