If Muhammad Ali didn't have a 3.5 year ban how would his career have looked?

As a long time champion, I think Ali gets an immediate rematch and ekes it out, as happened in real life.

After that he could do an earlier version of what he did after Spinks 2, retire and look on from the sidelines as Foreman destroys his two toughest opponents, Frazier and Norton, and then return to get the title back from him. After that it could happen very much as it did in reality. He wins tough/controversial rubbers against Frazier and Norton and makes a handful of other lacklustre defences before losing to someone he shouldn't lose to, maybe wins baxk the title, retires and makes yet another comebak, this time unsuccesful.

In the end he wouldn't quit for good until it was very clear he had nothing left.

 

To be honest, I do not think Joe Frazier beats him without the layoff. I do not think Ken Norton does either. And I think he outboxes George Foreman to a Decision win or late stoppage.

If Muhammad Ali had fought on after Foreman, he would, of course, have eventually lost. The Parkinson's and Age would have still caught up to him, perhaps even sooner than it did. Terrible disease!