I already shared Rolling Stone's list of the best movies of 1980. The magazine also shared their picks for the worst movies of that same year in that same issue.  For the most part I think their picks in this area have merit.  They are:

Any Which Way You Can
The Blues Brothers (this pick I do take issue with)
Caligula (I like this movie, but I understand why some wouldn't.  I do have to wonder if it made this list due to being made by rival skin mag Hustler.)
Cruising
Heaven's Gate (The archetypal bad movie)
The Jazz Singer
Raise The Titanic
Stardust Memories
Tribute
Xanadu (The disco roller skating movie no one was asking for)