Number 11, if this list were the top 11

Originally, this list was going to be like the previous one and include television, but the list became too unweildy and the choices too hard for this humble writer to make. So instead of filling this list with klingons, cylons (the original ones, as the new ones aren't technically aliens), the visitors from V (again the original ones, but this time because the new ones aren't as awesome), and ALF, I have restricted myself to movies. As always, I have other restrictions too: (1) if the alien appears in more than one film (including sequels, remakes, and reboots), that alien can only appear once; (2) Superman and similar alien superheroes don't count; (3) the alien has to have genuine extraterrestrial origins; and (4) the movie in which the alien appears has to have been out for at least a few years. So, with those constraints in mind, here are my picks for the top 10 aliens in film. If you think I left something out, got the order all wrong, am utterly insane, or am right on the mark, please let me know in the comments at the end.

First, though, come the honorable mentions: Clover (from Cloverfield), the aliens in Independence Day, the monolith from 2001: A Space Odyssey, and the "prawns" from District 9.

#10. STARMAN
Starman

Viewed by modern audiences, Starman is a cliché. The plot is about an alien who visits Earth in response to the friendly invitation included with the Voyager 2 spacecraft. The alien comes in peace and takes on the form of a human, the dead husband of a woman named Jenny. Of course, the alien is relentlessly hunted by the military and has to run away in order to get to his ship before it leaves him behind to die. Along the way, he learns the value and nature of human life, has inter-species relations with Jenny, and has an enlightening conversation with the peaceful scientist who is reluctantly working with the military and gives him just enough time to escape. The movie, in all honesty, doesn't hold up as well as some of the others on this list, but it is cliché these days only because it was such a poignant story when it was first told. As a side note, Jeff Bridges, who plays Starman, is the only actor to ever be nominated for an Academy Award for playing an extraterrestrial.

#9. MARTIANS
War of the Worlds (1951)

Regardless of whether you're talking about the 1953 film by George Pal or the 2005 film by Steven Spielberg, War of the Worlds presents a terrifying glimpse of how first contact with aliens might occur. However, like Starman, the story is painfully cliché by modern standards. In a nutshell, aliens invade the Earth and start eradicating humanity with their giant, robotic, three-pronged ships and probes. In the end, they fail to eradicate mankind, not because of mankind's resilience to the threat they represent, but because they were unfamiliar with our germs. It is a simple, but effective tale, with an ending that--while cheap because of the deus ex machina--makes it clear that humanity would stand no chance on its own merits in the face of an advanced alien species intent on wiping it from the face of the universe. Few seem to remember that the aliens are supposed to be Martians, but that's immaterial. I cite the 1953 version of them here because of the iconic sound the aliens made, a sound that still elicits chills and cold sweats from my inner child.

#8. MARTIANS
Mars Attacks!

Beings from Mars make a second appearance on this list in the form of the aliens from Tim Burton's cinematic masterpiece of irreverance, Mars Attacks!. The film manages to simultaneously honor and eviscerate genre tropes that have persisted from the 1950's to today in terms of alien invasion scenarios. However, the film wouldn't work if it weren't for the creatures themselves, playfully malevolent little green men with an ear-splitting language of barks and laughs and a desire to cause chaos that is as relentless as it is inexplicable. Whether they're transplanting the head of Sarah Jessica Parker onto a chihuaha's body, knocking over Vegas casinos, slaughtering all of Congress, or turning nuclear weapons into literal playthings, everything they do is for their own amusement, and you start to root for them because the human characters in the film are so painfully one-dimensional and stereotypical that there isn't a redeeming one in the whole lot, except for maybe Lucas Haas' good-natured donut salesman or Natalie Portman's cynical but abnormally cogent president's daughter. For dark is the suede that mows like a harvest, indeed.

#7. THE ANDROMEDA STRAIN
The Andromeda Strain (1971)

Most of the aliens on this list are terrifying, which speaks to what mankind typically thinks of the unknown. However, few of them can be called realistic, because when it comes to alien life, assuming it exists, we have absolutely no idea what to expect. The exception to this is, arguably, The Andromeda Strain, the film adaptation of Michael Crichton's novel of the same name about an extra-terrestrial virus that hitches a ride on astronauts and is let loose on Planet Earth. Of all the alien lifeforms here, the Andromeda strain is the least visible, intelligent, or complex, but it also strikes me as the most plausible. Over 99% of all life on Earth is microscopic, and if we assume that extraterrestrial life follows a similar evolutionary path to ours, it stands to reason that our first contact with aliens will be with alien microorganisms. This also presents an entirely different form of terror, because there is nothing in human experience as relentless, unmerciful, and uncontrollable as infection. Even worse, an alien virus like the one presented in The Andromeda Strain is likely to obey completely different rules from the ones we are used to, and that could easily devastate mankind much faster and much more efficiently than the most advanced alien warships.

#6. THE BODY SNATCHERS
Invasion of the Body Snatchers (1978)

1978's Invasion of the Body Snatchers is not the first or last film adaptation of Jack Finney's book The Body Snatchers, but it is, without question, the best. The aliens here actually come to Earth in the form of a gelatinous substance that quickly assimilates plantlife to form strange pods. These pods then start replicating people while they sleep, creating nearly perfect (but emotionless) copies and disposing of the originals. The copies then start seeing to it that the entire human population is replaced. What follows is classic paranoia fiction, ripe for symbolism and social commentary: in a world where anybody can be one of them, how can you know who to trust? In the 1950's version, the pod people are a stand-in for paranoid fears about communism, while the 1978 version is often considered a dark satire of "The Me Decade." It's a shame that the most recent film adaptation, 2007's horrid The Invasion, didn't try to tap into modern socio-political issues, because it would seem only natural to mine the story for "War on Terror" themes. Regardless, the body snatchers are a perfectly ambiguous creation, aliens that can represent almost anything we fear as a society at large, from the loss of individuality to the idea that there are aliens among us who want to destroy everything we cherish.

#5. THE PREDATOR
Predator

It is often hard for screenwriters to come up with the proper motivation for aliens. After all, they're alien, with alien values, morals, and intentions. This is why so many movie aliens are single-mindedly ruthless or high-mindedly compassionate, because those are easy motivations to work with. Every once in a while, though, a screenwriter will try something different, as Jim and John Thomas did for 1987's Predator. The title character, the Predator, is an alien hunter with a sense of honor. It uses a specific set of futuristic alien tools like a cloaking device and laser cannon to go after its prey, but it won't kill anything that doesn't fight back. Rather than killing for killing's sake--to eat or annihilate the way most evil movie aliens do--the Predator hunts for sport, and that makes it unique (or, at least, it did back in 1987, before people started copying it). Even though this is probably the easiest blood-thirsty alien to thwart (just put down your weapon and surrender), it's made all the more terrifying simply because you can almost understand it. Since it's motivation isn't so cut-and-dry, the predator is a nuanced, slightly sympathetic creature, and there is nothing we fear more than an evil we can relate to.

#4. E.T.
E.T. the Extra-Terrestrial

Though as an adult I firmly believe that Close Encounters of the Third Kind is a better movie, there's no denying the iconic charm of Steven Spielberg's E.T. the Extra-Terrestrial. Interestingly enough, the script for E.T. was being worked on by Columbia Pictures at the same time as the script for Starman. The studio decided they could only make one film about a benevolent alien coming to Earth and they chose Starman, letting rival studio Amblin Entertainment produce E.T.. The two films are far more alike than different, with the basic plot involving a dying alien with magical healing abilities trying to get home while being hunted by big government types who want to study it. Still, even though I still consider Starman worthy enough to include on this list, E.T. is more special because it takes on a more innocent tone. Spielberg wisely chose to film this movie from the point of view of a young boy, and in so doing, he highlighted the fantastical elements while downplaying the unrealistic ones. When he was finished, he created one of the most memorable and beloved aliens in the history of film (though, personally, I think E.T. might also be the most mentally challenged alien in the history of film).

#3. THE THING
The Thing

Surprisingly, when John Carpenter set out to make Starman, he was trying to prevent the end of his career following what was considered a nearly fatal flop, his previous film, 1982's The Thing, which was a critical and box-office failure. While both films are about aliens on Earth, the two could not be any more dissimilar in story or tone. Starman is set in the desert; The Thing is set in Antarctica. Starman is a benevolent being who wants nothing more than peace and understanding; the "thing" is a grotesque killing machine that uses the bodies of the dead to grow. Starman is a poignant, feel-good movie; The Thing is a horror film designed to keep you from sleeping peacefully. The Thing has stood the test of time far better than the more successful Starman, and for good reasons. It taps into many of the themes addressed by most of the other films on this list, including the paranoia of the body snatchers, the bone-chilling viciousness of the Andromeda strain, and the overwhelming sense of inadequacy represented by War of the Worlds. That's because the thing is, in a sense, all of them wrapped into one. It starts as a microorganism like the Andromeda strain, but it quickly develops into a shapeshifting multicellular creature capable of mimicking other lifeforms in much the same way as the body snatchers. Like E.T. and Starman, the thing only wants to go home, but it doesn't have the moral hang-ups of its more amicable cinematic cousins. More than any of the other alien on this list, the thing is the one that makes me squirm when I think what it would be like if it really existed.

#2. KLAATU & GORT
The Day the Earth Stood Still (1951)

One of the most common motifs in alien stories is the idea of judgment, that if we should ever meet an advanced alien species, the entire human race will be judged for its behavior at large. This is frequently explored in the sci-fi cinema of the 50's and 60's with varying degrees of success, with The Day the Earth Stood Still standing out as the most important exemplar. In the film, a humanoid alien named Klaatu emerges from a small spaceship on "a mission of goodwill," but is quickly shot by a nervous soldier. This is when Gort, Klaatu's robotic enforcer, enters the scene, immediately dissolving all the weapons in the area without harming anybody. Klaatu is then detained by the government but escapes, eventually managing to deliver his message to an assemblage of scientists: aliens are concerned about mankind's penchant for aggression and baby steps toward spaceflight. If mankind continues to make war, robotic soldiers such as Gort will be forced to extinguish every human on Earth. This was a particularly meaningful message for the time, because we had recently come out of World War II only to begin the nuclear arms race of the Cold War. It was felt by many that, if humanity could not overcome its own violent nature, we would launch our nuclear weapons and destroy the planet, with us on it. Klaatu and Gort, therefore, represent the socio-political angst of the last generation and are an important piece of fictional history that do not deserve their abyssmal remake.

#1. THE XENOMORPH
Alien

You knew this was going to be number one, so I apologize for being predictable. The fact of the matter is that there are no other aliens in the history of film that are as iconic, as memorable, as terrifying, or as truly alien as the alien, a.k.a. the "xenomorph." Though the xenomorph has undergone many subtle changes over the years, being animalistic one minute and more humanoid the next, its general demeanor remains the same. It is a hive-minded, relentless hunter with highly concentrated acid for blood and an extra, retractable jaw that can conveniently be used to punch through somebody's skull. It is born when an unwitting human gets mouth-raped by an aptly-named "facehugger" which plants an embryo into the human's chest cavity, from which the alien will explode at an unspecified moment in the near future. This disturbingly sexual, organic creature taps into something visceral and unconscious in the human psyche, and it is to outer space what Jaws is to the world's oceans, a terrifying beast that reminds us that the unknown can be a brutal, unforgiving place where forces we don't understand will tear us to shreds without the slightest bit of remorse. Hopefully, when and if the time comes that humankind meets an extraterrestrial lifeform, it won't look or behave anything like this nightmarish concoction birthed by the twisted imaginations of Dan O'Bannon, H.R. Giger, and Ridley Scott.