Unfortunately hasn't stood the test of time
It was groundbreaking on release, but it's too slow paced and uneventful for repeat viewings. Too many drawn out scenes that are only suspenseful on an initial viewing.
I was thinking whether this is due to the late 70's/early 80's era of film-making but there are plenty of movies that came out around the same time that are still as watchable today such as 'The Thing', 'Raiders of the Lost Ark' or Ridley's own 'Blade Runner'. As good as this movie was when it came out, it's a drag to watch today.