I grew up a sci-fi fanatic, so the defining movies of my high school days would have to be Ridley Scott's Alien (1979) and Blade Runner. The former transports the familiar gothic "house of horror," Hammer films formula to outer space with chilling, atmospheric results, while the latter is perhaps the finest example of cyberpunk film noir.
Although Blade Runner exploits its material and milieu to travel well beyond the boundaries of traditional film noir, to become a dark meditation on the human condition, the yearning to rejoin with one's creator, and what it means to be truly human. For which we have Philip K. Dick's feverish "Do Androids Dream of Electric SHeep to thank. But Ridley Scott must be lauded for packing so much dense, purely visual information and subtletly into this movie. I've noticed, though, that younger audiences tend to zone out at the film's deliberate (read: plodding) pace. Nevertheless, for me Blade Runner represents a high point in the short history of sci-fi cinema.