Sci Fi?
Good Sci Fi should allow us to see into the "plausible" future. My ratings would be:
Alien (plausible physics biology)
2001 (clever but a bit arty - farty)
Gattaca (quite close in DNA terms)
Solaris (1972 version Sentient force)
Blade Runner (draws on iRobot and takes it a bit further)
Slient Running (hmm they way we are going on earth!!!)
Metropolis (watch it. You'll see)
Matrix (not the best film but plausible)
I discount the likes of ET, Third Encounters etc as superseeded by Alien.
Stars Wars Star Trek and there ilk are out on known phyiscs grounds. The above list are also way better shot cinematically.