Good post!!Football statistics are incredibly subjective. Stats don't take into account the following:
Division - Each team plays 37.5% of their games against the three teams in their division. Each team also only plays against 13 of 31 teams, so schedule is a factor as well, but that tends to somewhat even out over the course of a career.
Location - Come November, you have factors such as rain, snow, cold, and wind to deal with up north. Dome teams and warm weather teams do not face the same elements which are more conducive to putting up numbers.
Your D - Does your D get you back on the field quickly allowing you to run more plays? A shorter field? Turnovers? Momentum?
O line - Is there an NFL QB in history who would have failed in the position that Troy Aikman was in? How about anyone who could succeed in the position that David Carr was drafted into? Most others are in a situation in between.
Your other skill players - What does a good RB do for a QB? How about a great WR? Daunte Culpepper was a stud when all he had to do was drop back and throw the ball up in the air anywhere in the direction of Randy Moss. Then there is always the TE safety valve that can really help sustain a drive on third down.
Cohesion between every player, every unit, every aspect is more pronounced in football than any other sport. Therefore, using numbers as a definitive evaluator is completely flawed. JMO.