Hmm... Well, Waterworld once held the coveted title atop my list but it has been replaced by the movie that will stand alone at the end of this post... And though I liked The Cube, it was still not a great film... Hollow man deserves honourable mention, but there are worse films... John Travolta, consistently terrible, disappointed everyone with Swordfish, it was dreadful, perhaps redeemed slightly by their rather creative visual representation of hacking (which is probably the farthest thing from actual hacking, but still looked quite spiffy) and of course, the lovely Halle Berry.
The thing with things like 'something about mary' and 'zoolander' and 'dude, wheres my car?' is that theyre not supposed to be good movies, although I loathe two of those three; theres something about mary being a movie I enjoy thuroughly
Granted, the Avengers was bad, but it had Sean Connery in it, and I just cant call movies bad where his delightful charm is present.
The award for worst ending ever: the new Planet of the Apes movie - continuity? Who the hell needs continuity!
Mr Brau hit the nail on the head though. Worst movie ever is Battlefield Earth. Hewson, also, with Jaws 4... Actually, any of the Jaws movies after the 1st one really... Sea World? What the hell was the shark doing in sea world? Pfff... Almost, AALLLLMOST as ridiculous as the shark somehow travelling 700kmph+ and waiting for the woman in the carribean... almost
Edit: Another honourable mention goes to Demolition Man, even though this is one of my favourite movies... cant really explain why though... its just so hokey that its endearing, and they actually put a whole half of their ass into making a plot, the dialogue is weak, and the acting is stiff, but its original, which gives it points above the others that are just recycling old ideas.