another way of stating the same is "he didn't fall short during but before even making it to any other potential SBs". Also, Trent Dilfer never lost a SB either while Peyton Manning has lost two. Does that make Dilfer better than manning?
Montana played in an era without UFA and salary cap, making it easier for big-market teams to put and keep together talented rosters. Today's NFL is built on the idea of leveling the playing field by making teams average thru and thru. Supporting cast nowadays is largely determined by the "revolving door" principle. Montana had HOF players like Rice around him, while even I can't name most of Brady's WRs without looking them up online.
Personally, I am no proponent of such comparisons when it comes to a team sport, from different eras, under different circumstances. This being said, it would be a lot easier to make a case for Brady being the GOAT than Montana.
This argument can go both ways, though. There were no quick fixes in the NFL back then. You couldn't throw money at a problem, so to speak. You had to do your homework in scouting, drafting, and making trades. If you didn't do your homework, you were dead to rights.
As far as Rice is concerned, Montana won his first two Super Bowls with Rice still in college.
His starting wide receivers in the super bowl against the Dolphins were Dwight Clark, Carl Monroe, with an over the hill Russ Francis as his tight end. He had Tyler and Craig as his running backs, but Craig was still unproven at the time.
His first super bowl offense around him was even worse, with the legendary Ricky Patton as their feature back.
So, he won Super bowls with his fair share of talent that could not be considered as all-star.
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I guess one thing that you could say in regards to the Montana vs Brady debate is the opposing quarterback that each faced in their super bowls, and in that regards, it's not even remotely close.
Ken Anderson, Dan Marino, Boomer Esiason, John Elway vs Kurt Warner, Donovan Mcnabb, Jake Delhomme, Eli Manning, Russell Wilson