Like all self respecting patriot fans I consider Brady as clearly superior to Manning and in a class with well basically Joe and no one else. In the last thread bashing Manning I made a list of my top 10 all time QB's and Joe was 1, Brady 2, and Manning 10. All of that said the people who rate Manning as highly as they do are not crazy or completely wrong, they just judge QB play on different criteria. Based purely on ability to throw the football, which is to some people (not me) the entire job of a QB Manning destroys Montana in every important stat.
Took the five mins to google stats off NFL.com
Manning 238 games played, 8,373 attempts with 5,475 completions for a 65.4%. 64,298 yards at an average of 7.7 yards per attempt. 483 TD's with 219 ints which is an int % of 2.6. All of that leads to a QB rating of 96.9
Montana 192 games played, 5,391 attempts with 3,409 completions for a 63.2%. 40,551 yards at an average of 7.5 yards per attempt. 273 TD's with 139 ints which is an int % of 2.6. All of that leads to a QB rating of 92.3
Manning has more completions then Montana has attempts
! Not to mention how much more durable Manning is having played in almost 3 seasons worth more games. For all the talk about how much more efficient Montana was they have the same TD:INT ratio which I was shocked to discover. So to sum up over an entire career Payton puts the ball up more, further down the field, for more TD's all of which say he is a better passer then Joe Montana and one of, if not the, greatest of all time.
So to answer the OP's point, no its not because he gets to piggy back Brady it's because his stats are INSANE and he still has another season or two to pad them.