The third Ali-Frazier fight s rightly described as one of the most exciting bouts of all time. What puts that extra sheen on it,was that it was fought in an exotic location,and had a nice poetic handle - 'The Thrilla in Manila' Supposing Ali had taken a third Norton fight in Manila instead of Frazier in '75 ? Would it have been immortalised so much ? I have my doubts. Main reason being,that although the three Norton fights were as competitive as the Frazier ones,Ali and Norton did n't have that antagonistic edge that Muhammad had with Joe.
That basically sums it up... Ali and Frazier were widely recognized as the other's chief opponent. In 1975, despite both having losses to other people, they were essentially battling for the right to be called the best of an era. A fight with Norton would not have set such expectations, though had Ken fought Ali and won, it would have drastically changed our hindsite view of the 70's.
Yes, not only was there not the intensity and rivalry of Ali-Frazier, but the styles of Ali-Norton never promised as much sheer brutality as Frazier brought. Norton was a lot harder for Ali to hit, and didn't throw as many punches as Frazier did.