I really don't have a big beef with the Brady-Montana comparisons as much, because I think both players are very similar. Montana was surrounded by some of the best offensive talent ever assembled, and Brady has been aided by one of the better defenses of the time period.
But the Manning-Marino comparisons irk me a bit. Marino went to a Super Bowl in his 2nd year, and IMO did more with much less than Manning has had. Marino, during his entire career in Miami, only had a 1000-yard rusher once (Karim Abdul Jabbar in 1996), and the Dolphins defense thru the 1980s was consistently among the league's worst. And at WR, Clayton, Duper, Fryar, and McDuffie were not in the same class as Marvin Harrison is/was. I'm not trying to say that Manning is not the best Qb in the league right now, because I believe he is, particularly with the decline in play of Steve McNair this past year. I will say that Manning is shaping up to be this generation's Marino, and I agree you can make comparisons, but too many people are going the extra step and putting Manning on the same plane as Marino, which I think is very wrong.
As for Favre, he's 1-1 in the Super Bowl, and although he's one of the toughest QBs to ever play the game, I wouldn't exactly put him in the same breath as Marino/Elway/Montana. I think it's pretty interesting that Favre's Super Bowl years, he had arguably the greatest defender of all-time leading that defense in Reggie White.
I just think that these 3 "golden boys" are slightly overrated. HOFers yes, but all-time greats? Not quite yet. I mean I'm excluded guys like Jim Kelly, Bradshaw, Namath, Unitas, Young, Aikman, Tarkenton, and Dawson, who I think in almost all those cases you could make an argument that any of those guys could be placed above the 3 aforementioned golden boys.
"Vincere scis, Hannibal, victoria uti nescis" -- Maharbal, 216 B.C.E.