The only caveat is that it isn't actually based on the movie Alien. The game I'm talking about is 7 Days a Skeptic, the second game in the Chzo Mythos series. I'll try to avoid any spoilers where I can, but some things I will say might be in a bit of a gray area. Also note that I'm talking about an Alien game, not an Aliens (or Alien 3) game.
These are some of the key traits of Alien that I think 7 Days a Skeptic happens to nail.
- Setting: They're both set on isolated/derelict ships being manned by a bare minimum of crew members.
- The antagonist/creature: Both 7 Days and Alien involve a single elusive, powerful, seemingly invincible monster loose on the ship, hunting down the crew. Both entities can show up and attack from out of pretty much nowhere, and run back into hiding just as quickly. And even though both creatures probably have the strength to be able to kill the entire crew all at once if the situation presented itself, they prefer to pick off the stragglers. On top of all that, both creatures were unknowingly/unintentionally brought on board by the ships' crews.
- Both ships, as mentioned before, are being run by skeleton crews. Every person has some crucial, unique role on the ship (none of them particularly qualified to fight back against a crazy killing machine), so shit starts going downhill quickly each time someone gets iced.
I feel like there are some other similarities, but those are the big ones I can think of right now.