A terrible disappointment and missed opportunity if there ever was one but it's not as bad as some people say. The game has an endless amount of flaws but there is some fun to be had. The graphics and story aren't great but if you like Aliens you will feel at home with the environments the devs have created. If they'd given the weapons more punch and the aliens a bit more brain, that would've done a lot. Fixing the now infamous spelling error doesn't improve the enemy-AI that substantially and therefore doesn't fix the brainless combat. The odd thing is, that there are sections where the aliens (must be other models, I suppose) act a lot smarter and are a genuine threat. They lurk behind objects, attack and vanish again. But the cannon-fodder-enemies they throw at you for 99 percent of the game are just an embarrassment to the brilliant creature H. R. Giger once created.
The fact that they tried to "fix" the beginning of Alien³ is a nice gesture to some fans (I don't care) but what they do with Hicks and Bishop isn't exciting either.
If you want to get terrified by an Alien game, play Isolation. As far as Alien-shooters go, try the marine-campaign from AvP2. That stuff is much more intense than any second of Colonial Marines. If you are lazy, like me, and just want to play a game that takes place in that universe and doesn't take much effort or dedication from the player, Aliens Colonial Marines is alright.