Couldn't we just broaden the definition - a good CEO takes a job that is difficult but achievable, a bad CEO takes a job that he's not competent enough to identify as impossible. I think a good example of this is Intel. Intel just spent a year trying to find a new CEO, but failed because no one qualified to do the job was incompetent enough to accept the job. All the candidates were competent enough to realise that job is going to be a blood bath.