I also think guys like Liston, Foreman and Bowe all missed great opportunities to achieve real greatness with perhaps big George probably the best of the three. Curry, Nunn, Breland,Camacho,Mancini and Zarate all come to mind who had every chance to be ATG but just fell short of the achievement.
Maybe Mosley has missed out too with his losses to Forrest, Wright and Cotto.