During the ad campaign for Prometheus, I knew someone who thought it reminded him of Alien. My friend and I told him that it was indeed part of the same franchise and his excitement quotient jumped considerably.
Another one of my friends didn’t realize it until he was in the theater watching it with his girlfriend and the Weyland corporation was brought up.
Fox probably thinks they’d be throwing away money by not explicitly connecting the title this time around.
Based on the evidence, they’re probably right.