Like all "greatest" conversations, it depends on your criteria.
If Rodgers won 2 more Super Bowls and MVPs, it wouldn't matter because he is perpetually boring if not outright unlikable. He's at his most likable when he's being himself, at least the arrogant and show-boaty side.
If he played in SF he would be exactly like Kaep and taunt and talk shit all of the time, except he could actually read defenses.
That being said, Favre will always be the greatest Packers QB. His legend will only grow from here even if the truth is that he and his team were perpetual underachievers.
Starr was a good, serviceable QB, can't see the argument there. I guess there's the Lombardi connection but he'll always be overshadowed by Lombardi.