'Prometheus' Set to Hit Theaters: The 10 Greatest Film Aliens of All Time

Ridley Scott's Prometheus is one of the most anticipated films of the summer. The Alien prequel, in theaters Friday, will face competition from another alien flick, Men in Black 3, a week into its release. Since the dawn of filmmaking, aliens have invaded the big screen, with varying success. Here's a look back at the 10 best extra-terrestrials in movie history.