For the vast majority of NFL teams, “the greatest quarterback in franchise history” played sometime within the last 30 years. The passing game has advanced leaps and bounds in that era, so it makes sense.
There are exceptions, of course — you could argue that the Cowboys and Steelers have to go back to the ’70s to find their all-time QBs in Roger Staubach and Terry Bradshaw, though Troy Aikman and Ben Roethlisberger are certainly in the neighborhood in more recent times. It has definitely been that long for the Vikings, who have had random old men like Randall Cunningham and Brett Favre put up excellent numbers in their Minnesota stop, but arrived too late to be compared to Fran Tarkenton.
With all due respect to Ray Lucas, only the Jets fall all the way back to the ’60s with Joe Namath. And though 1940s slinger Sammy Baugh is probably still the greatest QB in Washington history, Sonny Jurgensen and Joe Theismann weren’t too shabby in more recent decades.
For the Chicago Bears, the conversation has always begun and ended with Sid Luckman. He hasn’t thrown a pass since 1950.