Unsurprisingly, there have been a large number of direct adaptations of the Aliens franchise with wild variations in quality (even between platform ports). For example, the Amiga and Apple IIc version of Aliens are pretty different, as are the Sega Genesis and SNES versions of Alien 3. As far as good Aliens-themed games go, the general consensus seems to be Alien vs Predator 2, Alien: Isolation, and the original DOOM total conversion mod. I've also heard positive things about the Nintendo DS title Aliens: Infestation, but I haven't had a chance to play it myself.
Incidentally, during the pre-production of Alien 3, H.R. Giger did a bit of design work on the alien for that movie. Not wanting to simply repeat himself, the artist added some new features to the creature such as a "finger brain," consisting of numerous tendrils along the top of the head that would movie in rhythmic patterns. Additionally, his new alien design had hollow tubes that would emit haunting windpipe noises. I don't know how scary this would have been on film (none of he designs were used because of concerns over production costs), but it's bizarre stuff, totally unlike anything found on the planet Earth. Hence, "alien" in the truest sense of the word. I can understand why filmmakers would be reluctant to take those kinds of risks, but if you're going to make a tie-in game you might as well try to make it stand on its own merits.