I have not played FPS games much, but this was an exception despite the dated graphics. Darkness and the lighting work well in the levels which are too maze-like. The movement speed is high which makes feel that you are controlling a hovercraft rather than a person. There’s no even footsteps.
The marine gameplay is quite typical FPS but with a survival element. Watching out the fast aliens in the darkness, and relying on the motion detector. Makes the gameplay intense at its best, but sometimes frustrating with sudden insta-kill moments like the facehuggers. And the final boss battle was unclear to finish. The guns are effective but there is no button to reload gun. And you cannot get your guns to the next episodes.
The predator gameplay is a mix of shooting and stealth. The weapons are otherwise cool, but the melee hits with the wrist blades have no clear feedback. The invisibility is quite unreliable because the human enemies can still detect you even further away. The predator cannot jump high like in the later AVP games, though the levels are mostly monotonous corridors. Speargun ammo recovering would have been a nice feature, and collecting the enemy skulls too.
The alien gameplay is unique being able to climb across walls and ceilings, having fast-paced stealth action and recovering health from the kills. The enemy detection is quite unpredictable, and the alien does not have stealth gimmicks. You can hiss to lure enemies and even to scare them, though they can still shoot you. An acid spit would have been good idea and bleeding acid blood on floor for as temporal traps. The facehuggers do not appear in this campaign. A missed opportunity: having facehugger minions.
And there are not much AVP games around besides this one these days.