Invasion of the Body Snatchers" (1956)
The “Citizen Kane” of 1950s science fiction films, the original “Invasion of the Body Snatchers” is still the best. Based on the Jack Finney novel “The Body Snatchers,” the story should be familiar to anyone semi-literate in film. It centers on a doctor (Kevin McCarthy) whose patients insist their loved ones have been replaced by imposters. It appears that people are being replaced by perfect duplicates grown in pods who are identical to their human counterparts but lack all emotion. Widely seen as an indictment of McCarthyism, the film works as both paranoid thriller and political allegory (the best ones usually do.) Watching the film today, it’s amazing to see the way this movie walks the line between many genres (noir, sci-fi, horror) without ever stepping into silliness. Despite the opening/closing bookends shoehorned onto the film by the studio, the ending (featuring one of the best examples of breaking the 4th wall in cinema history) is still chilling. "They're here already! You're next!" A true classic. [A]

Lifeforce" (1985)
Most alien invasion movies are defined by flying discs, but Tobe Hooper's "Lifeforce" is most fondly remembered for a pair of orbs -- namely, the breasts of lead actress Mathilda May, who spends most of the movie walking around completely naked. The production, which was co-written by "Alien"'s Dan O'Bannon, infamously ran over-budget and was marred by disagreements in the editing room between Hooper and his production company, the dearly departed Cannon. Not that this explains anything you see onscreen. The movie has some bright spots, for sure, including a typically jaunty Henry Mancini score and an admirable lead performance by the underrated Steve Railsback, but it's mostly a mess -- an unintelligible mishmash involving space vampires, Haley's Comet, and lots of hot alien nudity. Even Hooper's considerable stylistic flourishes can't save this from being little more than a late night oddity. [B-]

Mars Attacks!" (1996)
The cinematic landscape in 1996 was punctuated by a pair of big budget, heavily hyped alien invasion movies. "Independence Day," with its easily digestible gulps of rah-rah patriotism, was released that summer and made bucketfuls of cash. Tim Burton's "Mars Attacks!," released several months later, was defined by its prickly cynicism and more or less bombed. Which is a shame, really, because there's so much to love about ">Mars Attacks!" -- from Jack Nicholson's Peter Sellers-esque dual performances as the President and a Las Vegas sleazebag, to Industrial Light & Magic's Harryhausen-y visual effects, to the fact that Warner Bros. made an $80 million event movie based on a series of scummy, hyper-violent trading cards. (At one point the movie was rated R and was considerably more expensive, thanks to Burton's insistence that the creatures be stop-motion animated.) Maybe audiences weren't ready to see the end of the world played out as a large-scale cosmic joke… or maybe they just thought the joke wasn't that funny. [A-]