I agree with many of the choices made here. Disagree as well (I like SW chapters I and II, stilted dialoge aside).
The campy sci-fi hooey films of the fifties, the go-go/biker bad girl loops of the sixties, etc. have reached a sort of cultural icon status....MST3K has taken them as far as they can go. The bad slasher/gore stuff of the last 30 years is par for the course (is there actually a good film here?). What's left for unique badness? I am not really sure but here are a few of the most unenjoyable movies I have seen for what it's worth..
Sgt. Peppers Lonely Hearts Club Band (the worst musical ever concieved, much less actually made)
Born American (American college kids escaping from a Soviet prison - that alone would have been enough to end the pitch if I had been at that power lunch)
American Beauty (every bad PC Hollywood sexual stereotype fully fleshed out and presented with 8th grade creative writing class level symbolism)
Deathwish (Bronson created the pointless revenge genre with this one. If you think about it, it is quite a feat of acting to instill in the viewer a complete lack of sympathy for a man whose wife and daugher are raped and murdered.)
Hook (Rivals Sgt. Peppers in the "why the hell was this story ever created" category.)
Jurassic Park (We've got the superstar author and we've got Microsoft Softimage, we simply have to make a movie....no let's make 3!)
I know I can dig up more if I try, but these I remember with an immediate alka sletzer recall - I can't beleive I watched the whole thing.
Thanks,
Rob