I'm not sure sure this adage applies as well to games as it can to films. Sometimes a movie can be so inept in its production that, whatever its original purpose (usually horror), it ends up being hilarious. A similarly inept game, however, would probably be incredibly frustrating to play.
Everyone's examples so far seem to be either games that are somehow outrageous and taboo, or are only subpar in storyline, dialogue or other areas not directly tied to gameplay. That's fair enough. Hilariously bad story or voice actors can enliven an experience. Has anyone here played Space Siege? It tries to ruminate on the question of what defines a human being by giving the player the option of gradually replacing more and more of your body with cybernetic enhancements. Their approach to what was supposed to be a deep philosophical question was so ham-handedly one-sided that I immediately decided to go full cyborg just to spite the writers. The female lead's poorly-acted disgust at my new metallic groin was hilarious.
Disregarding that tangent, my original point was that in games, these aspects are often second-fiddle to gameplay (excepting rare circumstances where gameplay is actually secondary to the story, such as Heavy Rain). I would still call the games you guys have suggested good games, even if their stories are silly. A bad game is one whose gameplay has failed to interest the player, and I think that is less likely to amuse than a bad movie.