The Thing (1982) vs Alien (1979)

Love both, but I'll go with "The Thing" (1982).

Close call, but Alien is my favorite horror film.

I vote The Thing. It’s a much more relatable scenario because it’s taking place in current times on earth. The cast is absolutely great and them never really knowing who is or isn’t human is really what builds the tension. The killer being in the blood also really connected with audiences in the early 80’s because of the AIDS epidemic at the time as well. Knock out score also! I vaguely remember the one from Aliens.

Alien, although both are excellent.

Alien. It's an essay on horror and fear converted into a gripping thriller. The Thing is great, but not that great.

EDIT: By "not that great" I meant "Not Alien Great", not that The Thing was not *that* great. It's a great film. Don't jump down my throat.

PS
Yes, that was a facehugger joke.

The Thang (2018) !

The Thing.

Alien, obviously. For one, it has a much better cast and acting. The direction and cinematography are also better. The characters are actually somewhat defined and have a backstory to them, instead of just being cardboard cutouts. And the design of the Alien itself is iconic. The story is also original and not just a remake of another film, and has more intriguing plot elements.