I think the key to a good bad movie is “I want to make a movie but I haven’t got any money” or “I want to make a movie but I don’t know what I’m doing” rather than “I want to make a movie but I can’t really be bothered to put any effort in”.

Take Plan 9 From Outer Space. There’s a certain amount of charm from seeing a guy hide his face the entire movie to hide the fact that he’s clearly not Bela Lugosi, the UFOs being hubcaps on fishing lines, or the fact that all the cockpit scenes appear to be in somebody’s shed.