This Island Earth" (1955)
It's honestly quite impossible to think of this rather dated '50s sci-fi with a mindset not tainted by "Mystery Science Theater 3000"'s various quips and witticisms, though maybe that's a good thing. Rex Reason, whose name alone is source of heated debate, stars as a scientist in this tale of aliens recruiting humans to help them in their intergalactic war. Of course there are more sinister plans at hand, such as a complete relocation of the alien community to planet Earth and the ultimate brain-reprogramming of the two main characters. However, it's not as exciting or dire as the plot description suggests, and instead we're mostly subjected to a derivative romance between two plain-pizza actors with a spaceship or two thrown in for good measure. The fact that their relationship helps convince Exeter, the lead alien, to sacrifice himself for their safe escape is almost as unbelievable as the pair not knowing that he and his buddies were extraterrestrials from the beginning, if only because they have foreheads that can only be measured in Ricci. It's certainly not as awful as most MST3K movies can be, but despite its nostalgia-fueled defenders, that doesn't mean it's good either. [D+]

War of the Worlds" (1953/2005)
The DNA of H.G. Wells' 1898 novel "The War of the Worlds" can be found in virtually every film on this list: the seminal, and arguably first, alien invasion tale is endlessly influential, and quite frankly a better story than most here. It was first adapted by Orson Welles in a legendary radio production that threw the country into terror (we'd have killed to have seen a film version from the master), and Ray Harryhausen planned an aborted version in the 1940s (watch his test footage here), but it was '50s sci-fi great George Pal who was the first to bring Wells' novel to the screen. His version, which shifts the setting to then-contemporary southern California, still impresses; it's head and shoulders above its B-movie contemporaries with effects that hold up today and a genuinely chilling Cold War-infused world view. The religious subtext unravels the film a bit at the end, but it's mostly terrific. Steven Spielberg's more recent version is less memorable, rife with the third-act problems that have troubled most of the director's work in the 21st century, but the first half remains strong -- Spielberg uses the imagery of the 9/11 attacks in a way that brings genuine horror to the invasion, a horror lacking in many of its contemporaries. [1953 - A-, 2005 - B-]

Honorable Mentions: We've barely scratched the surface, particularly of the '50s, when the flying saucer B-movie was at its most prevalent: "Invasion of the Saucer Men" and "It Came From Outer Space" being two of the best-known, along with "Kronos," although the special effects in the latter were hardly cutting edge even at the time. Ed Wood's "Plan 9 From Outer Space" became legendary as the so-called "worst film ever made," presumably by those who haven't seen "Transformers: Revenge of the Fallen."

"Gremlins" knock-off "Critters" has been sullied by its umpteen sequels, but the original is fairly entertaining. Philip Kaufman's 1978 take on "Invasion of the Body Snatchers" doesn't quite match the original, but comes very close, particularly in Donald Sutherland's excellent performance, and it's certainly far superior to Abel Ferrera's 1993 "Body Snatchers" or the troubled 2007 Nicole Kidman vehicle "The Invasion."

And then there were the extraterrestrial visitors who weren't quite mean enough to make our list. Perhaps the closest is the original "The Day the Earth Stood Still" (stay far away from the Keanu Reeves remake); a bona fide sci-fi classic, but probably not quite malevolent or large-scale enough to qualify as an invasion. Steven Spielberg's been the master of the kindly alien genre -- "Close Encounters of the Third Kind" and "E.T." both feature space invaders with more benevolent intentions. Both are worth rewatching before you head into "Paul," a conscious tribute to those films in particular.

Drew Taylor, Cory Everett, Kimber Myers, Oliver Lyttelton, Gabe Toro, Christopher Bell, Mark Zhuravsky