Unless it's something with an extraordinarily good squad-based system (with decent AI to match), the only way to differentiate it from becoming yet another 'Doom' clone with 'Alien' set design is to allow an Alien single-player campaign (or even just exclusively that). Otherwise, it's just another human-running-around-with-guns thing and those have essentially been ten a penny for decades. Even if the presentation of 'Colonial Marines' had been polished up, it would have still been left with that problem (which would have meant it was effectively going up against the 'Call Of Duty' and 'Halo' games).
'Isolation' has defined itself by going down the alternative route of making you helpless. Not sure that can really be sustained for terribly long before the novelty wears off, though. Most people purchase these things because they want to feel empowered, not play as a victim. And you'll notice even that title has apparently realised it needs to force you to face off against synthetics and such, to spice events up.
