The aliens need "Signs"
"Signs"
Why it's so dumb: So many sci-fi fans have heard this one that it's almost bad form to mention it, but the blunder is pretty simple: Aliens navigate the vastness of space and find life on a puny planet. Then it turns out they need cornfields on that puny planet to point them to fresh meat. The only thing that made sense about the scenario is that the aliens wanted to eat Mel Gibson first.
Why we don't care: As every sci-fi fan can tell you, "I want to believe."
John Hurt feels better, so opts for breakfast
"Alien"
Why it's so dumb: "Oh, thank goodness the acid-blooded crab thing fell off my face. Hey, do I smell scrambled eggs?" Despite a ship full of highly-intelligent technical and science people, the crew of the Nostromo decides not to quarantine their alien-toting buddy long enough to make sure there were no problems along the lines of, say, stomach erupting alien babies.
Why we don't care: A hundred space horror movies later, including three more "Alien" flicks, a lot don't remember how terrifying "Alien" was in 1979. And while the movie was good and creepy up to this point, the "man gives birth" scene was the moment when the movie went from just scary to the scariest movie you had ever seen.
Skynet sends a new and improved Terminator
"Terminator 2: Judgement Day"
Why it's so dumb: There were at least 50 smarter, easier alternatives to whacking Sarah Conner and her unborn son other than sending back the hit-machine to the land of big hair. And after screwing up the first time, why would they try again after Sarah has had years to train both herself and her military mastermind child? How about sending a good old T-1000 back to Sarah's great, great, great grandmother's house around 1880? What would Kyle have used to fight? A musket?
Why we don't care: The relentless pursuer is a suspense theme predating the written word, and for good reason. "T2" felt like high-budget vindication for all of us who actually saw and enjoyed "The Terminator" the first time around.
Will Smith uploads a virus to save the world
"Independence Day"
Why it's so dumb: "Independence Day" had already lost all credibility when Will Smith climbed into an alien spacecraft and after a few moments, figured out how to fly the thing. But dumb turns to laugh-out-loud ludicrous when Will conquers the aliens with a floppy disk, in an absurd homage to "War of the Worlds." Will should have just stuffed a peanut butter sandwich into the disk drive. It would have had the same odds of working.
Why we don't care: Because we like absurd homages to "War of the Worlds." Part of loving sci-fi is recognizing moments that only other sci-fi fans will recognize. The only thing better would have been if Orson Welles did a voiceover for "virus uploading" rather than simply seeing the words on the screen.
Dr. Brundle tries out his fly machine
"The Fly"
Why it's so dumb: Jeff Goldblum's character is smart enough to defy physics and biology in every conceivable way, including appearing attractive to Geena Davis, but he isn't smart enough to keep his equipment free of household pests. But honestly, that's not the dumbest part. The dumbest part is that he rationalizes ever stepping into the thing. If Goldblum's "Jurassic Park" character were there, he would have said, "Don't be an idiot," and the movie would have been over.
Why we don't care: "The Fly" was a movie with the world's easiest gimmick: Watch a guy turn into a fly. There should be more movies like this. Watch a guy turn into a lobster. Watch a guy turn into an oyster. This is what science is all about.
Velociraptors come off like geniuses
"Jurassic Park"
Why it's so dumb: Jaws was a thoughtless eating machine and scared the swim trunks off of us, so why did we need dinosaurs fresh from the debate club? The book read perfectly well with the dinosaurs just being very, very hungry. The raptors, despite having acorn-sized brains, seemed to have no problem navigating a vast building they'd never been in before in order to corral Sam, Laura and the kids in the lobby. Maybe the T-Rex came in and ate them just for their severe lack of credibility.
Why we don't care: You'd be challenged to find a single person from the "Land of the Lost" generation who didn't love some part of "Jurassic Park." And besides, it was nice to see the computer generated image technology put to use in a ways other than aliens and terminators.
Agents throw punches at Neo
"The Matrix"
Why it's so dumb: Anything that happens to you in the Matrix happens to you for real, right? Thus verifying the theory that if you die in your dream, you're really dead. So why then do the Agents decide that shotguns and kung-fu are the best way to take out Neo? If the Matrix is such a savvy computer, wouldn't, "Neo is in New Jersey, good-bye New Jersey!" be a pretty obvious solution?
Why we don't care: Most sci-fi fans had read William Gibson's "Neuromancer" many years earlier, and "The Matrix" finally helped visualize what the hell was happening in that book.
Superman turns back time
"Superman: The Movie"
Why it's so dumb: This is the classic problem with any time travel plot. If Superman can turn back time, why not turn it back a few years, find Lex Luthor, and break a few fingers? Instead, Superman turns back the clock just enough to save Lois from a not-so-shallow grave.
Why we don't care: Actually, we do. This one is just too dumb.
Jodie Foster and company pass the alien MENSA test
"Contact"
Why it's so dumb: Intelligent creatures from across the universe go to great lengths to let humanity know they exist in an otherwise great movie called "Contact." Life from distant galaxies intelligent enough to capture our rays, translate them, then dramatically send us the blueprints for a wormhole machine, somehow found it necessary to put those blueprints on a flattened piece of origami.
Why we don't care: "Contact" was (finally) the insightful and thought provoking sci-fi movie fans had waited more than a decade for (with all due respect to "Species"). And most fans removed their Vulcan ears in honor of Carl Sagan while watching it.