Prometheus is tough call. Does the average person even know the movie has anything to do with the Alien series? The advertising doesn't really seem to sell that part.
I don't know, for anyone who's seen the Alien movies, that movie certainly has the same look.
The only question is, will people:
1. See that, recognize it, and go to the theatres because of it
2. See that, think it's trying to rip off Alien and skip it
3. Completely miss it