There is no debate in my opinion. People who try to argue that he was a great "passer" and not a great "quarterback" are those who do not have any clue about the game of football. Last time I checked, the primary job of a quarterback is to "throw" the football. Quarterback's are not there to takcle people, intercept passes, block, catch.
A great quaterback is the type of guy who is a field general, that takes charge of a game, which Marino was the best at. A quarterback fires up his players, which nobody had that "look" in his eye like Marino, and you know when he had that glare, that the other team was in trouble.
A quarterback leads his team down the field, and scores. Nobody put up the numbers like Marino, past or present. Numbers do not lie, and you can not argue his stats. He has the 2nd best winning percentage in NFL history, only 1 win behind the all time leader in Elway.
Just because he does not have a ring on his finger, does not count against his ability as a quarterback. He was the best at that position in NFL history, and the only other guy that you can even possibly argue that comes close to him is Elway.
Football is the ultimate team game, and guys like Montana and Brady were drafted onto solid teams with great coaching, players, systems, etc.
Neither of them carried a team on their back, like Marino did for over a decade. Those guys just happen to be on great teams, therefore have championships.
If you compared those guys to Marino as far as a quarterback goes, and just based it on that, neither of them had or have the skills of Marino.
Nobody could pick apart a defense better than Marino, nobody could read the blitz better than Marino. Nobody could thread a needle between 2 defenders better than Marino, nobody could put that touch on the ball like Marino. And nobody threw a better pass than Marino. Those are all the types of things you have to take into consideration when measuring a quarterback. Not just..." oh well so and so has rings, and Marino does not" That is just flat out stupid to try and compare a player simply on the fact if he has won a championship or not, especially in football, the greatest team game in sports.
Bottom line is, Marino is the greatest "quarterback" in NFL history.