Alien: In space no one can hear you scream.

Alien continues the 1950’s obsession about contact with life from other planets and the mostly horrific effects it ends up having for humans.
HR Giger’s design for the xenomorph is what makes Alien a cut above the earlier films and the imitators that would try and use the same formula for success (and usually fail miserably.) You look at it and know that it might have burst from the chest of a human, but its origin was not earth. The creature plays into two big fears that a lot of people have: bugs and the unknown. It also has aspects of body horror, since the xenomorph gestates inside a human host. Though there are only hints of it in this film, later ones in the series delve deeply into the idea of a horror coming from inside your own body.
In this film, we don’t know what, beyond killing the crew, the xenomorph wants, if it wants anything at all. It might just be killing the crew because they’re there. While this lack of motivation only adds to the mystery of the monster, it does point out something as well. The alien is more like an animal than a truly malevolent creature, like say the Predator would be. It’s not overly smart or even very cunning, it just hides and when people find it, kills them. It’s a nicely done Lovecraftian monster in that humans can’t interact with it except as its exterminator or its prey. We don’t understand it, there’s no way to reason or talk with it, and if you don’t kill it, then you may end up as an incubator for more of them.
The life cycle of the creature is the only understandable thing about it. It kills people, but we can’t even be sure that it eats them. It’s entire ecology is a mystery, and we can’t even be sure where it’s from originally, except somewhere in the darkest reaches of space. While we see the Queen in the next one, Alien is just one monster versus a whole bunch of people who are unprepared for the assault and have to find ways to deal with it and each other. There’s lots of talk of shares and money and what the crew is going to do with it when they get home. Once the facehugger attaches itself to that unlucky bastard, all that kind of thinking goes out the window and it becomes a struggle for survival. Even then, the crew has more unknowns than just the xenomorph to worry about.
It’s difficult, having watched all the other movies and read a bunch of the novels and comics, to keep straight what the film tells us about the creature and what all the other movies and things add to the mythology. What’s cool is that you can kind of see where the seeds (or eggs?) of the future installments were planted in this film, even if it wasn’t exactly known whether there would be more or not.
There’s about a million imitators of this film, from the absolutely cheesy, like SYNGENOR, (which was filmed in a hotel) to fairly decent stuff like The Abyss and Leviathan, (which is one of my favorites. I love the last line, which is yelled as Peter Weller of Robocop lobs a grenade into the mouth of the creature, ala Jaws “Say hi Mother____.” All of these films try to tap into the central themes of Alien, either in the same way or with twists and turns in the plot and storylines. This isn’t a sub-genre that’s going away anytime soon.
And then there’s the actual Alien sequels and the books and the toys, (I still sort of want an original Alien figure, though I have a deluxe Alien Queen that’s pretty damn cool.) and their ill-fated meeting with the Yautja (or Hish), what non-geek folk call Predators. The first comic AVP series from Dark Horse is pretty amazing, it’s light on people and heavy on monster vs monster action. The first AVP movie, while filling in some interesting plot points from Alien (we meet the Weyland in Weyland-Yutani, or the Company) didn’t really deliver enough monster mayhem, because for whatever reason, the movie people thought we needed a total rehashing of how the xenomorphs spawned instead of just dropping all three species onto a planet and letting us watch the blood and acid and green blood fly.
In a rather strange coincidence, my current mentor, David Bischoff, wrote Hunter’s Planet, book two in the Alien vs Predator novel series.
While some people may turn up their noses at it, Species is another movie that uses Giger’s designs and has sort of a similar theme of aliens perpetuating their races by using humans as nurseries, or in the case of Sil, extra DNA to produce a true mate.

And then, there’s this:

alienlovespredator.com/2010/06/02/cash-cab-time-machine/

alienlovespredator.com/2010/05/05/happy-smothers-day/