There is only one position that has a W-L record in the NFL. Do you think that at least Earnest Byner deserves a L for fumbling away that playoff game to DEN?
There is really no way to measure QB to QB unless they play under the exact same circumstances with the same team, which isn't possible.
I watch QB's play and assess their skill set, particularly under pressure, and decide whether that's a QB that could make a good team better. He can only help the defense by not making mistakes that put them with the short field to defend. He can also score so much he takes the opposition out of their game plan.
If we're talking about Prescott, and when aren't we, I have little doubt he could take a good team to the Big Dance. I have felt that way about Stafford and feel they're the favorite now to represent the NFC. I felt the Patriots were actually a better team, even missing the key pieces, than the QB. HOU has a better QB than the team.
Give me the choice of an elite QB or elite D and I'll take the D 10 times out of 10. An average QB like McMahon, Dilfer or Johnson can be elevated by a great D. You take the elite D down to an average one from Bart Starr, Terry Bradshaw, Joe Montana, Troy Aikman and Tom Brady and how many rings now?