This could be true.
Think about it: The NFC has budding QB stars coming up: Rodgers, Wilson, Kaepernick, Ryan.
But all the AFC has is Brady and Manning who will be done VERY soon. And an up and coming Luck and a constantly injured and also old Roethlisberger.
Flacco gets to the superbowl and maybe wins it, the AFC has a new star QB for the future.
Edit: Don't forget RG3 and Cam for the NFC