Duey, I must disagree with both you and your father-in-law.
Namath was not one of the greatest QBs ever, but he made a guarantee and backed it up in possibly the biggest upset of all time. He was the first QB to throw for 4,000 yards in a season (in 1967), but he's also the only HOF QB to have more INT's than touchdown passes.
He was simply a good QB, yes, but he didn't make his whole career on Super Bowl III, though at times (and to Jets Fan), it may seem that way.
Mike