OH MY GOD IT'S LIKE COD ZOMBIES WHAT A RIPOFF!
I have to admit, you can throw a wave-based survival mode into almost any game, and I'll be happy. I've always got time for that particular game type, and the inclusion of Xenomorphs just makes it all the more perfect.
Here's a video for Colonial Marines' spin on the idea. As you may have guessed, it's got a team of four marines, facing off against encroaching hordes of slavering bugs. You can earn points, upgrade, unlock doors -- all the usual jazz that idiots will say is a ripoff of Call of Duty: Zombies, despite the fact that Zombies didn't invent any of it.
So yeah, enjoy!