"Alien" ... the original (Ridley Scott) ... haven't watched it in years, but it hasn't lost a thing. Truly a masterpiece of suspense ... the amount of time you actually see the creature is maybe 180 seconds, tops, yet it is more suspenseful than any of the others, (they went more the way of "horror" in the sequels, I think ... horror and action, (loved the first sequel, too, though).