I was entranced as a kid with the 1953 movie "Invaders From Mars." I was six at the time. It stayed in my memory, and when VHS came out, it was one of the first tapes I purchased. After watching it, I was a little let down, because as a kid, I think I built it up to be more than what it really was. The part that haunted me was when the people would walk out to the end of the rail fence, and then just drop out of sight.
Another good sci-fi movie is "Quatermass and the Pit" from 1967.
*****
Still a good flick today.