You people are all listing "Popular movies I didn't like." That is not the title of the thread. It is worst movies ever! I don't care if you don't like Napoleon Dynamite, it is most certainly NOT the worst movie ever made. None of the movies named here come even close. These are movies that actually made money in the box office. That should immediately disqualify them. Try some of those lowest ranked on imdb. Manos: The Hands of Fate is highly touted as THE worst movie ever made. Unfortunately, I have yet to get my hands on a copy, but from the description, the reviews, and the facts about the movie, I will probably agree with the assessments I have read.
Here are some movies which are worse than pretty much every movie mentioned on this thread:
Lake Placid - so unintentionally funny I couldn't stop laughing the entire time. It was hilarious.
Hell Comes to Frogtown - starring Rowdy Roddy Piper. Low budget 80s movie about post-nuclear apocalypse. Sam Hell (Roddy Piper) is one of few fertile males left in existence. He needs to rescue the fertile females (also rare), enslaved by the mutant frogs who have taken over the earth, and impregnate them. One scene in particular is great, where they show a character falling off a cliff. The mat he lands on is CLEARLY in the shot and you see the edges rise up as he lands on it. Everything about this movie is just so bad it's great. My favorite line is, "Yeah, I agreed to f*** for freedom" - Sam Hell.
Anyone naming Titanic or Napoleon Dynamite doesn't know the meaning of "bad movie."