I saw this movie when I was about 12 when it came out. I recall the scariest scene was the big bird eating men dangling helplessly from parachutes right out of the air. The horror. The horror.
As a young kid going to these cheesy B films on Saturday afternoons, I still was tired of the formula for these monster type movies that usually included the hero, a beautiful woman who might be the daughter of a professor and a happy resolution when the monster died in the end. I didn't care much for the romantic angle as a 12 year old and the predictable plots. I love them now for the unintentional humor.
But, about a year or so later, I saw Psycho when it came out and I loved that the star, Janet Leigh, was bumped off early in the film. I sat up and took notice at that point. Since screenwriters are making up the story, make it up to be as scary as possible and not from a well-worn formula. There are no rules.