Originally Posted by Gradstudent78
Similar to Alien or similar to Promethesus?
Depending on which movie I'd say the closest things I can think of are The Thing, Pitch Black, Signs, War of the Worlds (All basically Sci-fi horror involving Aliens, most of which are not as polished or necessarily as good)
The Thing is a very good film, and the 2011 prequel very under rated too.
While not an alien based film, Sunshine is a great space sci fi, and Event Horizon is a good space horror.
If you want to see some of the themes of Prometheus (evolution, alien life and the evolution of artificial intelligence) 2001 A Space Odyssey is a superb film.