First off, I believe the poster was referring to the Nicholas Cage stinker 'Season of the Witch' that came out a few years ago.
'Halloween III' on the other hand IS NOT a crappy movie. People just can't get past the whole "no Michael Meyers" part of it. If you can actually forget that, it is an effective 80's horror film. They intended to expand on the 'Halloween" franchise after Michael Meyers and Dr. Loomis were supposedly killed off in Halloween II and planned on releasing a Halloween holiday themed film every year using the 'Halloween" name. Fans, of course, couldn't get over the no-MM thing and the film tanked and has been forever labeled a bad horror film, when it is anything but.
To answer the OP's question, my list of bad horror films is extensive, but a few of them that top the list for me are 'Troll 2', 'Fear Dot Com', and the Rob Zombie 'Halloween' remakes.