It was not awful, imo. It was great!
It is not a prequel, but set in the same universe. Ridley said so himself.
Well, not a direct one at least.
I expected this movie to explore ''Space Jockeys'' and suggest how humans were created, and it did.
Movie leaves a lot for viewer's imagination.
As a fan of Alien ,I've ejoyed bits of connection Prometheus had to it : Wayland Corp, Android...
I went to see it expecting little to no horror scenes and even invited my not horror fan parents, boy was I wrong inviting them XD