"isnt that what almost all alien movies are 'bout?"
wat.
No, Predator = Earth, Alien = space. That's how they should be in the movies. And i agree with Stalker, the distant planet setting is the best for AvP games. Large population scenarios are best for RPG's not for FPS's. I think a game in the style of "Stubbs the Zombie in Rebel Without a Puls" would be interesting for aliens. Where you can somehow take facehuggers along with you and build an army of drones, from the enemy humans, following you as you grow larger and are able to use new attacks.