While pondering the question of which cartoons should not be made into live-action movies, my initial snap judgement answer was "all of them", because I haven't seen one yet that didn't disappoint me in some way, even though a few have had some entertainment value.
So I'll amend my blanket moratorium, and say no movie based on cartoons featuring anthropomorphic or talking animals, especially if they interact with human characters. Some of the worst movie ever made fit into this category: Garfield 2, Rocky and Bullwinkle, The Cat In The Hat. I haven't seen Underdog yet, but the trailer alone make my sphincters clench with involuntary pain, so I'm not getting my hopes up.