John Reynolds said:
Xanadu is still the worst movie of all time.
I'd say either "On Deadly Grounds" with Stephen "Woodface" Seagal or "Cyborg III" are good candidates for worst movies ever.
Some movies score points on being so bad they become funny cult classics. Well, neither of my candidates fall into that category. Stephen Seagal's movie has some dumb injun dream hokey-pokey magic shit in the middle somewhere with eagles flying and stuff, and then he holds a really corny speech at the end about saving the environment after having blown up half of alaska with soot-and-dioxin-spewing gasoline explosions. As usual, he keeps the same stony Judge Dredd-like expression throughout the entire movie. When his face sort of twitches a little, that means he's trying to show, "oww, that hurt".
Cyborg III has this doped-up steroid broiler chick carrying big guns in it. Like Arnold in his early movies, she has about 3 lines sum total. Actually, I think she says, "nothing clean, right", "fuck off asshole" and "what's your address there?", and that's it. Also, she keeps changing her belt all the time, I think she wears like fifteen different belts. The writer and/or director obviously has some kind of kinky belt fetisch going because this is really really weird.
Also, both of these movies are insanely boring, precluding them from being a laugh-fest. Only way you'd laugh watching them is if you drink yourself to death and then return as a ghost and understood you died watching a POS movie like that... Probably means you actually committed suicide rather than finish watching it.