For your consideration: a 1982 faceoff: John Carpenter's THE THING or Ridley Scott's BLADE RUNNER.
They also came out on the very same (Fri)day in June 1982, sci-fi's ultimate film year. Myself, I saw BLADE RUNNER once it dropped into my local multiplex, but I wouldn't get to THE THING until it came to video half-a-year later. BLADE RUNNER achieved classic status first, probably by the time of its 1992 re-release. Despite its budgetary limitations at its end, I now prefer THE THING.....which definitely is wicked fun in a way BLADE RUNNER couldn't and never wanted to be.
But what if you could only see one? In 1982, I went with BLADE. Now, I have to vote differently.