I don't think PM is in the conversation, though I'd still put him in the top 5.
It's just that, as I'm reading these discussions (on the ESPN board, NFL.com, etc.), the only thing people are talking about are SB victories & appearances.
IMO, there's a difference between "the greatest" and " the best" which is what makes the discussion so subjective. There have been a lot of fantastic quarterbacks. Most people measure "greatness" by accomplishments over time. When the debate is looked at from this perspective, it's virtually impossible to deny Brady the top spot as he's clearly the most accomplished quarterback of the modern era.
Having said that, it doesn't necessarily mean that he is clearly the "best" QB of the era. Without question he's clearly one of the best but making a case for Montana, Marino or Manning is doable as it's all subjective.
There are things that those three QB's did better than Brady which may put them ahead on someone's list if those things are important to an individual who is ranking these guys.
Personally I'd take Brady over those three but the margin is slim. I think that Montana, Marino and Manning are all distinctive quarterbacks. They are like great guitarists. You recognize who's playing within a few cords and that's true for those three.
Brady is different. He's more of an amalgam of the other three. Brady doesn't throw the soft catchable ball of Montana, the Marino bombs or have his insane release or have the otherworldly ball placement of Manning.
He did have, and still occasionally displays, Marino's incredible pocket presence while improving on his quick game prowess. He has Montana's presence and ability to patiently kill great defenses with simple repetitive concepts while also stepping up huge in the most pressure filled moments, and he has Manning's uncanny ability to streak through halves, games and series of games and occasionally full seasons which drives opposing players and fans to hatred.
Personally I don't feel that either Marino or Montana were nearly as consistent over the length of their careers as Brady or Manning have been. And neither Marino nor Montana could carry a team over a full season the way Brady and Manning have in their careers. Those two have never really had an off year if you give Manning a mulligan for his rookie effort. Montana had some pedestrian years and Marino was downright careless with the football tempering many of his great seasons which can't be said about Brady or Manning.
My personal rankings aren't much different than anyone else's. I think that Brady and Montana's superior play-off performances & pedigree separates them from Marino and Manning.
I believe that Brady should be ranked ahead of Montana not only due to greater team accomplishments but because of the success Brady's teams have had when they had no right other than his performance in many cases.
Where Manning and Marino most often wilted under the hot lights of the play-offs, Brady has most often thrived. Six late drives in Super Bowls, machine like performances in division round game after division round game, coming up huge late vs the Raiders in 2001, late v Rams in XXXVI, late v Carolina in XXXVIII, v a 15-1 Steelers team that had previously crushed the Pats in the 04 AFCC, a monster effort to knock off a far superior Chargers squad in 2006 with a team that had no business even being in the game, those late SB drives v the Giants and those two monster drives against the Seahawks set Brady apart from both Marino and Manning and their frontrunner pedigrees.
Other than Manning's effort in the 2006 AFCC game comeback vs the Pats, when has he put either the Colts or the Broncos on his back to pull out an improbable play-off victory through grit and will? How about Marino?
It's closer between Montana and Brady of course. Both are far more accomplished than the other two team-wise. Both have late game play-off pressure credentials which are legendary. Brady has been a more consistent performer and he's been more versatile.
Montana was Montana, excelling in a west coast system built on quick passing, a strong running game, possession tight ends and outstanding two and three receiver sets.
Brady has excelled under a wide variety of base offenses and no QB has ever had to handle game to game offensive changes like Brady has and with the success he's had doing it.
I think these small things, greater team accomplishments, so many improbable victories against great odds, superior consistency and excelling in so many different styles of offense puts Brady above Montana on my list. That I'm a Pat's fan doesn't hurt either.