The game managed to rake in a ton of preorders, and the Aliens name is a strong one, so I'm not surprised it sold well. I'd be interested to know how many of those sales were traded in shortly after the transaction, though. Even to the hardcore Alien fan, it's not exactly a keeper.
The positive side to this situation is that it at least proves the strength of the Aliens brand. It's still obviously a hot seller, and that's why SEGA's been so keen on keeping the games coming. Hopefully this means we'll get more chances at a good Alien game, and maybe some decent backing for the mystery title Creative Assembly's working on.
The negative side, of course, is that it feels like Colonial Marines exploited the built-in goodwill toward the Aliens IP, and potentially harmed it with a short-sighted grab for cash. It infuriates me to think that this game might sell a ton, burn customers, and later damage the chances and potential of a future, better game. Not that it seems those responsible for this garbage care too much.