Tough choice, both represent excellent early works from Ridley Scott and James Cameron, and both pushed the boundaries of the Sci-Fi Horror & Sci-Fi Action genres. Alien is more unique and broke new ground with a lead female protagonist with a deep focus on tension,mystery, horror and the feeling of isolation and the unknown.

Aliens on the other hand, dialled the action upto 11 and focused on character relationships/ world-building and the effects that the Alien creature had on the colonists. We begin to understand more about the creatures breeding habits and the fact that a Queen exists as if they are like a hivemind. I would give the edge to Aliens, but only by a smidge.

Both are good. Aliens is better. I am actually surprised the poll results are this close. I guess there are a lot of people who prefer the style of the first movie.

The poll is neck and neck. It's a tough choice for sure!

Alien vs. Predator 1. The rest in both series make me want to pour tarter sauce on my eyes.

The first is more refined in building up tension and developing the whole plot and characters, for my tastes it's slightly better. The sequel is great too, anyway, and Lance Henriksen is excellent.

Resurrection was for me where the series effectively died, which is a shame as it had some interesting ideas and fun characters,