Remember Ryan Leaf ?
Leaf's problem wasn't that he isn't good, it's that he was thrown to the fucking wolves... had he been on this years charger team, he may have taken them all the way... The team wasn't as dominating then.
Oh, and for what it's worth Brian Griese really is a very good QB, when he was in Denver he had many flashes of brilliance... unfortunately, Denver is another team you can count on to send you out to the Wolves and not have your back if it doesn't go your way.
That's where Peyton has been fortunate, he had a few shit ass years too, but no one ever held him accountable and the Colts never turned their back on him.