Well, either that was an easier question than I thought, or there are some really good players out there! Everyone who guessed got the right answer!
1956 was the first movie made from the serial novel:
1978 was the remake without a hopeful ending:
1993 saw the military base remake:
And Nicole Kidman starred in last year's version:
According to IMDB, in the 1978 edition, only 3 people knew how the script ended, so when Veronica Cartwright's character runs into Donald Sutherland's character and he does the alien scream, she was truly shocked and the camera caught her actual reaction.
New question on Saturday!