Aliens: Colonial Marines puts you in the boots of a colonial marine returning to the Hadley’s Hope colony. The actual game is supposed to be a sequel to the Aliens movie. You should be seeing some very recognizable scenes from the movie in the game. Drop-in/Drop-out co-op mode is available for the single player campaign or you can go it alone. The game is being published by Sega and was developed by Gearbox, who is known for Borderlands and Brothers in Arms.
At the moment Aliens: Colonial Marines is slated for a Spring 2012 release on PC, Xbox 360, and Playstation 3.