Hard for any movie to have such an impact today, mainly due to the constant leaks, making of's, clips showing key parts of the movie and marketing etc.
Back in 77 I went to the movie and had never even heard of it. I was worried it was going to be a war film and it would give me night-mares!
These days I parctice good film-hygiene to try and enjoy movies more.
I watch no trailers, news items, teasers or anything for a movie I am interested in. Nothing. Then I go see it as early as possible.
I am enjoying movies far far more than I had been over the past few years. It makes it so much more enjoyable when you haven't already heard the lines, seen the effects, know the twists etc.
I think it is why I enjoyed Tron Legacy so much more than my peers, I kept myself in the dark and knew nothing except the images on the posters. It was so much more impressive that way. It was like being a kid again.