Just read through this whole thread, chuckling at the re-emergence of that age-old "bad movie or YOU just don't like it?" argument. Fun stuff.

My own defintion of a truly BAD movie is this: you sneer when you think of it, and you CERTAINLY wouldn't watch it again.
Anaconda is a
stupid movie. Some say it's also
bad. But I enjoyed its stupidity, so therefore I'd watch it on cable one night.
If
I am Sam or
Patch Adams came on cable one night...I'd spend the evening alphabetizing my vital organs.
I feel no need to constantly re-state the overused acronym of "IMO". If you're reading a post with my name on it, odds are you're seeing my opinion. If I say a movie is "unmitigated crap", you can feel free to add an IMO to it if need be. I discovered early on that there is rarely a "right" and a "wrong" when it comes to the appreciation of movies. I could tell you that
Spun is easily the worst movie of the year, but then you all know that I love movies entitled
Popeye,
1941,
Deep Blue Sea and (yes)
Armageddon. Opinions are like assholes; you should take 'em with a grain of salt.
I could look at Fairuza Balk and see a true beauty. I have friends who think she's horrifying. Doesn't mean I know more about "beauty" than they do. It just means I have better taste in women.

So with those pointless introductions, I offer what "I" consider to be...
The Worst Movies Ever Made...although it's really hard to make such a distinction without having SEEN every movie "ever made". So consider it...
The Worst Movies Ever Made Based on the Several Thousand That I've Seen Thus Far in my 31.6 years on Earth (not counting infancy)Patch Adams - The all-time reigning king of hatefully manipulative dreck. I couldn't possibly loathe a film any more passionately.
I am Sam - Patch's retarded little brother. Bad because of its blatantly push-button agenda-baiting. Atrocious because one of our finest actors sinks to playing handicapped for the Oscar Bid...and it worked.
Ringmaster - Makes me nauseous just thinking about it. Springer spends 80 minutes in depraved muck; spends 4 minutes at the end trying to rationalize it all. If alien beings do get our TV broadcasts and they come here thinking that Jerry Springer and his guests represent mankind...we'll be dead in about 12 milliseconds.
Batman & Robin - I hate to play "pile on" with all the really popularly loathed flicks, but great gosh a'mighty does this one deserve it. So amazingly garish and misguided that it simply boggles one's mind.
The Doom Generation - Yeah, I "get" what Araki's slingin' but I ain't buyin. You like mindless shock value? Give it a spin. Be prepared to need a
long shower once it's over.
For Richer or Poorer - The Amish don't watch movies, so clearly they're fair game for the unbelievably moronic stupidity that they're objected to here. Tim Allen and Kirstie Alley, for some odd reason, chose to play their leading roles as the
most unpleasant people ever to be born, which makes the horrrific "make nice" finale all the more pathetic.
Boxing Helena - Oooh. Pretentious absurdity without the craftsmanship to pull it off. Nepotism contributes to one of the biggest "howlers" I've ever seen.
Flowers in the Attic - To this day, I mention this movie to my mother and she gives a sad little sigh. She loved the books. Good lord is this a bad movie.
Gone Fishin' - The worst sort of broad comedy: talented people given nothing to do and they do it loudly. So unfunny it hurts to watch.
Tarzan the Ape Man,
Bolero and
Ghosts Can't Do It - John & Bo Derek are to cinema what hydrochloric acid is to human flesh.
The Haunting - One of the most unnecessary, least entertaining and most dramatically inert remakes ever created. I felt like I was watching an empty house for 90 minutes.
...anything with the word
Howling and a number in the title...
Kazaam and
Steel - I got nothin' against Shaq. Just keep him out of the movies. This double feature could cause blindness in small children.
Leonard Part 6 and
Ghost Dad - What are the odds that one of the world's finest comedians would star in two of the least amusing comedies ever made? It's uncanny.
Listen to Me - If you count this one as a comedy, it's quite good. Between Kirk Cameron's Southern Drawl and a plot devoted to the intricate workings of a
debate team, your brain won't know what to do with itself.
Mannequin 2,
Problem Child 2,
Arthur 2,
Caddyshack 2 Blues Brothers 2,
Weekend at Bernie's 2 - Good god make it stop.
Nothing But Trouble - I've always had a lot of respect for Dan Aykroyd...this movie notwithstanding. Plotless, ugly, incoherent, totally unfunny. Demi Moore's got nice cleavage tho.
The Mangler 2 - Makes
The Mangler look like
Battleship Potemkin.
Yor: The Hunter from the Future - Even before I really knew what a BAD movie was, my friends and I mocked this flick to no end. "No,
you're the hunter from the future!"

See also:
Metalstorm: The Destruction of Jared-Syn and
Megaforce. Or better yet, don't.
My Father the Hero and
Blame It on Rio - If you've seen both of these, you probably know why I lumped 'em together. Just...ick.
...anything with the words "Children" and "Corn" in the title...
On Deadly Ground - As an action star, Seagal is totally unconvincing. As a tree-huggin' environmentalist who ends his movie by preaching
directly to the audience...he's just insufferable. Calling something 'the worst Seagal flick' is the diametric opposite of high praise, and that's precisely what this one is.
Benigni's
Pinocchio - Definitely earns some pluses for its production design, etc. but then loses several more points for Roberto's horrific portrayal of a keening puppetboy. One of most unintentionally creepy flicks I've ever seen.
...any
Police Academy movie with a colon in the title...
Rad - Looks like it was filmed with a Handycam and six dirt-bikes. I hear it has a cult following of some sort. Don't tell 'em how bad this movie is.
Showgirls - I have a few friends (even ones who are critics) who think that the U.S. "missed the boat" on this movie and that it's an underrated and crafty social satire. I think those guys are freakin' nuts. This flick only stops being boring when it wants to say or do something amazingly ugly. I detest this movie.
Slapstick (of Another Kind) - Sit all the way through this one and I'll shake your hand. Mind-alteringly awful.
Snow Dogs - The bottom of Disney's Barrel O Formula...and that's pretty low indeed.
Sphere - Makes the
Congo adaptation look like
Treasure of the Sierra Madre.
Wicked Stepmother and
Saturday the 14th Strikes Back - Try watching these two and then tell me that
2001 or
Deliverance are "awful movies".
...anything in which Ashley Judd or Jennifer Lopez "fights back"...
Bad Boys 2 - Yeah, I honestly think it's one of the worst movies I've ever seen. The contempt for the audience is simply outlandish...and this is coming from a guy who has repeatedly
defended Michael Bay's excessive style.
Baby Geniuses - Easy target...for good reason. You can feel yourself getting stupider as it goes on. And there's a sequel on the way. Yay.
...just about anything with either Martin Lawrence or Cuba Gooding Jr. in a lead role...
Collision Course - There's a good reason you don't see this Jay Leno flick pop up on cable too often. He probably bought all the prints!
Not many controversial choices, I know. Hmmmm. What do I hate that lotsa people love? Oh,
Top Gun. Hate.
Rambo: First Blood Part 2. Hate!
OK, I'm rambling.
Ooh..
Wired. Now there's an awful movie!