Stan Helsing was alright, better than Epic Movie or Disaster Movie.
The worst film I have ever seen was a film titled "Santa and the Ice Cream Bunny" It is so awful that it has a small cult following. Here is a youtube link to check it out. The quality sucks but so does the movie. Lol
Most of the mainstream films that are mentioned may be awful, but they still look decent, go for some of the old films from the 70s and before. You get some stinkers there. If you want to see amusing films that are awful, look up some movies by a company called the Asylum. They produced the wonderfully done "Snakes on a Train", "Transmorphers", "Mega Shark vs Giant Octopus", and "The Terminators". There are a bunch others out there by them and most are awful but usually amusing.