Some of us use the term bad movies to mean, simply, films that emerge from ๐ a supposedly lowbrow genre, or films that are stylized in the manner we tend to label camp. (Road ๐ House from 1989 is this kind of bad movie, and is very good at being one.)
There is no single "most important" element as all film components ๐ story, characters, acting, direction, production quality, pacing, emotional impact, relatability, and originality contribute to its overall quality. However, ๐ many argue that a compelling story is at the heart of a great movie.