He has 3 super bowl rings.
He also lost in two of them and failed to make any more despite having arguably the most talented team in the league around him.
He has the all time record for TD passes in a season.
He barely got that record over a guy named Manning so many of you are ready to bash. Nearly half of those TD tosses came to one player, too, but let's not give him any credit.
He has the all time record for most post season wins for a QB.
If this was all I knew about him, it would tell me a couple of things:
First, he didn't play for the Cleveland Browns over the last decade or so.
Second, he was blessed to play for a team that had talent to work with him (i.e. again, not the Browns).
Third, he didn't cost his team any games.
Other than that, there would be no way to know how much of the TEAM'S success he is actually responsible for. But we'll take your tactic and assume he won all the games by himself.
Football outsiders ranks him as the best QB in the league 4 out of the last 6 years (3rd in 2011, injured in 2008)
They also say he's comparable to Trent Green, and not a single person here has even made one mention of Green as being great.
In his career he's thrown for 334 TDs and almost 45,000 yards with a 63.7 completion percentage.
So he's had a long career as a starter.
What failings could he possibly have that completely offset all of that?
Considering most of what you just said is relatively meaningless in terms of establishing his greatness, any mention of his failings at all more than offsets it.