It’s a surprisingly controversial subject among fans. Eight licensed feature films form the franchise, and there are some areas of common consensus. For instance, it is unlikely anyone is going to storm the comments if we say we can disregard the Alien vs. Predator movies for reasons of them being bad.
An area of less certainty is the Prometheus/Alien: Covenant duology. Directed by Alien’s Ridley Scott, you would think these had a cast-iron claim on canon-hood, and yet disregarding the films’ problems, they don’t feel like they are interested in the things that a proper Alien story is interested in.