Alien worked because of Sigourney Weaver’s iconic Ellen Ripley. She was a normal person like you and me, who found enormous inner strength when thrown into the middle of the ultimate claustrophobic nightmare, with nowhere to run. There were no giant, rolling spaceships. There were no screaming, alien-ooze-infected zombie attacks. There were no deus ex machina squid monsters to save her. There was a woman and her fear, and nothing to save her but her wits and an indomitable will to survive. She was the opposite of the Xenomorph, the opposite of the murderous android, Ash. Ripley was human, and she embodied the very reason why scientists wouldtravel to distant worlds to find out who and why we are.
Prometheus has no Ellen Ripley, no humanity, and as a result, says absolutely nothing about us worth hearing.