I've seen many a bad film in my day, and there are a lot of films that compete for the title of "worst film ever." 'Plan 9 From Outer Space' is most frequently cited as the 'Citizen Kane' of bad movies, but in my opinion, that was easily Ed Wood's best film. The worst I've ever seen is 'Turkish Star Wars.' You know how people say, "so bad it's good?" Well 'Turkish Star Wars' is so bad, it's just really bad. No redeeming value there.
I would recommend the Vanilla Ice vehicle 'Cool As Ice.' It is probably the worst film I have ever seen that is still worth watching. It is GODAWFUL, but there are some quality laughs provided by its artistic abhorrence.