I see what you're saying. And, quite possibly, I see Brady not as causing as deep of a storm as he does in NE. However, that's also because they've basically have had the exact same coaching staff since he started, so it is difficult to state.
Manning, somewhat can get the same treatment. He went to a team with all-star talent. Broncos weren't scrubs, they simply needed a decent passing QB, which they didn't have with Tebow (obviously). If he went to, say Chargers, then would he be as successful? I don't think so, he's not mobile and can take hits but not for that long. Most of his throws come from the bottom random than the top, legs vs arms, so to speak.
Now, Brady has the same problem but can adapt faster because of his quick decision making skills, and, consequently, ability to get rid of the ball fast as fuck. I would argue the best in the league in that component. So, I can see him adapting to that situation very well.
Let's use a good team with a lacking true QB (as a secondary 9ers fan, I believe in this wholeheartedly). Replace Kaep with Manning, does Manning thrive? The oline is decent, not good enough (or at least this season) to establish pocket presence. And let's not forget that Manning doesn't necessarily like utilizing the run game. The guy loves to pass, or his coaches simply abuse him in that aspect of the game. Due to this, he throws a lot of interceptions, compared to Brady. Should be added that he and Brady do attempt just about the same number of throws per game, and he still makes a lot more mistakes than Brady does. And let's not forget that Brady has been sacked way more than he could imagine.
So, from this, who would be more successful on this, basically, perfectly built team? I'd say Brady. He's thrived with bums and all stars, while Manning mostly only knows all stars. Never has a receiver been made because of Manning. He has favorites and they're most always fantastic players. As much as I love Julian, he's not a great player. He has chemistry with Brady and so they feed off each other. Lafell is not that good but you can't really tell. Manning uses established stars, and I'll argue that he can only use established stars, and succeeds because of it. Always in the perfect offensive situation. Brady, not so much and still succeeds with an incredible consistency rating. Now, this can be because of administrations but still. Using strictly personnel, we see which player works better with new situations. Denver was simply Colts 2.0 in terms of personnel, offense, and structure.