I think the older a film gets the more suspension of disbelief is required, you have to want to buy in to the world the film creates. Much more so for sci-fi, fantasy etc. I think if you enjoyed a film “back in the day” it’s much easier to suspend your disbelief and relive the experience of watching it.
I love watching The 7th Voyage of Sinbad, Clash of the Titans, Jason and the Argonauts, Sinbad and the Eye of the Tiger every time they are on TV. I love the artistry that went into them and I still remember how terrified they made me as a kid. My wife just laughs at them and thinks they are ridiculous hokey old crap.
http://www.bbfc.co.uk/releases/alien-0
You mean Alien the 18 rated film?
It’s worth mentioning that Alien was rated “R” in the states since it’s release ie
“Under 17 requires accompanying parent or adult guardian. Contains some adult material. Parents are urged to learn more about the film before taking their young children with them.”
So under 18s have been watching it since it’s release over there. Hopefully, no one died.