I'd say it does tell its own story AND knowing at least about the first Alien really helps. MAYBE the more recent prequels help, or at least the first one, but I'd think it can be enjoyed without all of them. My oldest enjoyed it and has only seen Alien, Aliens, and Alien 3 before.
I can't remember which ones I have or have not seen and there is no way I could tell you where each fit in the timeline.
Does it stand in its own if someone has only seen a few or none of the other Alien/s offerings?
I'd say it does tell its own story AND knowing at least about the first Alien really helps. MAYBE the more recent prequels help, or at least the first one, but I'd think it can be enjoyed without all of them. My oldest enjoyed it and has only seen Alien, Aliens, and Alien 3 before.
Currently on IV!