Sure, you are comparing regular reasons stats between 12, 14 and 16 game seasons. To move in the direction of a reasonable stat analysis you would have to go to per game...which would be a small step in the right direction.
And you don't seem to understand the rules changes issue. While QB's may have gotten mauled in the past, the sack did not become a stat until 1982. IT was the WR's who were really getting mauled before '78 because you could bump them all the way down the field.
You also seem to take some things into account in the reverse of what is logical. You discount some of Montana's success because he had good defenses and good running backs. I think that is arse backwards.
A better example might be Bradshaw, for most of the 70's he played on a team with a historcially good defense and two top notch backs (I think they might have been the first pair to go over a thousand yards each in the same season). So for most of his career he would never had needed or had the opportunity to throw the ball as often as say...Dan Fouts or Brady. Have a look at the attempts per game of someone like Brady, or Manning and compare that to Bradshaw or Unitas or someone from that era. The career totals of Brady and other modern quarterbacks are sure to be higher (especially the way you look at them) for someone in the modern era who will a) play a 10% longer season (at least) and will have a much larger number of attempts.
QB rating is also flawed. It rewards the dink and dunker over the long ball thrower. If I go three for three for nine yards and my team punts, I get a higher rating that if I throw a 40 yard completion and then three incompletions and have to punt. But who has done better for their team?
And your stats don't take into account running in any way.
Here is a great article showing why it is impossible to meaningfully compared stats even from the 80's and 90's to today. It was done in the Tebow/elway context but lists a few recent changes in rules that impact the comparison.
http://www.milehighreport.com/2011/...lacy-of-comparing-stats-across-different-eras
And then there is the large increase in Yac on an ongoing basis that balloons modern stats...
Addendum:
Here is another interesting chart for passing attempts per game average:
http://www.pro-football-reference.com/leaders/pass_att_per_g_career.htm
Now how can you fairly compare Bradshaw (23.2 per game) to Brady (36.7). I guess for starters you could double Bradshaw's passing numbers...it all gets silly in a hurry.
