I understand you guys are talking about bad companies, but in terms of a bad cartridge label design, "Off the Wall" is probably the worst Atari put out.
It looks like it was done with colored pencils, not to mention the art itself is just terrible. From that damn flaming "M", to the distressed Japanese guy with the bent wrist, it's just hideous.
And a little bit more on topic, Froggo games aren't that bad, they "are" playable.
Mr. Postman has to be the crappiest game I can think of. Also Joust isn't too much fun.