He was in the top 10 QBs for his entire career and was in the top 5 most seasons and was a pro bowler/all pro for about half his seasons. His stats in the 80s look pretty pedestrian compared to modern passing numbers, but it was a different era and he spent a lot of years playing in a Dan Reeves offense that was predicated on running the ball into the middle of the line for no gain on 1st and 2nd down, then hoping Elway could pull some bullshit on 3rd and long.
Joe Flacco, by comparison, has finished in the bottom half of the league passer ratings more than he has finished in the top half. He's typically been about the 20th best QB in the league at any given point.