@Ice_Ice_Brady - nice work. You obviously put a lot of time and effort into it.
The fact that various decades are represented at the top of the rankings gives this list much more credibility than the majority of "best all-time" lists that appear periodically. Those tend to be far too heavily represented by current or recently retired players.
Comparing players across different eras is an extremely challenging task. The fact that you have adjusted for passer rating based on the year is a big step towards resolving that issue.
Some in this thread have mentioned wins, playoff wins, etc. If that metric is going to be used then it too needs to be adjusted dependent on the year. The number of regular season games played as well as number of playoff games has had several alterations.
- 1926-32: 11-14 regular season games; no postseason
- 1933-60: 10-12 regular season games; one postseason game
- 1961-65: 14 regular season games; one postseason game
- 1966: 14 regular; max two postseason (first super bowl)
- 1967-77: 14 regular; max three postseason (two playoff games, plus the SB)
- 1978-89: 16 regular (15 in '87); max 3-4 postseason games (two wild card games)
- 1982 (strike): 9 regular; four postseason
- 1990-2019: 16 regular; 3-4 postseason (playoffs expand from 10 to 12 teams)
- 2020: 16 regular; 3-4 postseason (playoffs expand from 12 to 14 teams)
- 2021: ?17? regular, plus 3-4 postseason games
The point being that a change in rules and the way games are officiated is not the only difference resulting in passer stats increasing. Going from a ten to 12 to 14 to 16 regular game season, as well as going from one single championship game to four games between 14 teams, that too will alter number of wins and won-lost percentages. These factors also apply to comparisons and rankings of franchises and other positions across various eras. The playoff wins in particular are difficult to compare; it's almost like you should add two wins for anything prior to 1965.
One tool I have found to be useful when comparing players of different eras is to see where they ranked each year in various statistical categories. To me it creates a far more meaningful picture than raw stats do. It also helps explain how Vinny Testaverde retired with the 6th most career passing yards in NFL history, and Kerry Collins was 9th.
Philip Rivers is an example of the above, and where current era players benefit not only from rules geared to the passing game, but also those rules resulting in longevity - thus larger career numbers. Rivers retired with the fifth most career passing yards, yet was in the top-5 in passing yards only one-third of his 15 years as a starter. In 2006 Rivers ranked 9th with 3,388 passing yards; that number would have put him at #19 this past season.
One caveat to the yearly ranking comparison above: keep in mind there were fewer teams back then, so the further back you go the less meaningful a high ranking is. Ranking fourth in the AFL meant you were average, since it was an eight-team league. For that group it is more along the lines of ranking 2nd then equals 5th now, 3rd=9th, 4th=13th, etc. Same goes for pre-merger NFL, with 16 or fewer teams.