Your argument that a championship should not determine a QB rating has merits. Look Montana is remembered for his Super Bowls but not all his playoff losses. Manning and Breese have benefitted from playing indoors. Also different teams run different offenses so the argument to switch Brady and Manning has flaws. So in judging the best QB ever, maybe one needs to ask this question. Your team is down with little time left. You need a winning drive or otherwise you lose. But the problem with that question doesn't address what offense you are running. But that being said my Uncle who knows his football thinks we are all idiots and claims Johnny Unitas is the best of all time.