I don't think Ali really became "The Greatest" until the second half of his life, after he was diagnosed with Parkinson's Disease in 1984. He continued to live his life with dignity and courage, courage that surpassed that of all other boxers who might be contenders for "The Greatest." At the memorial service, Bill Clinton gave a moving description of how Ali had to struggle to light the cauldron at the beginning of the 1996 Olympics:

http://abcnews.go.com/US/bill-clinton-recalls-muhammad-alis-final-steps-light/story?id=39764535