It's impossible to rank the greatest records in sports history. There are just too many variables, too many skills that are difficult to compare, and too many eras to compare them across.
That shouldn't stop anyone from trying, though. It's tremendous fodder for bar conversations and arguments with drunk friends.
So here's an argument I'd like to present:
If anyone attempts to make a list of the greatest accomplishments/records in sports, and Cal Ripken's consecutive game streak appears anywhere on that list, Brett Favre's record of 253 consecutive starts at quarterback has to appear ahead of it.
No disrespect intended to Ripken, but a quarterback will have more opportunities to get injured in one series than a baseball player will in a couple of months. I don't mean to trivialize the physicality involved in baseball, but ... well, actually, I do. It's a fine sport, but compared to the NFL, it might as well be synchronized swimming.
For Ripken's record, it was more about mental toughness and attitude than it was an actual ability to take a beating. Both Ripken's and Favre's records stretched across 16 seasons. I'd say that makes Favre's mental toughness equal to that of Ripken's, and as far as physical toughness goes, there's really no comparing the two. I doubt Ripken ever felt the morning after a game how Favre feels on your typical Monday morning.
There are other arguments to be made in opposition of Favre having the most impressive longevity record in sports. There are two NFL players with longer consecutive game streaks. One of them is a punter (Jeff Feagles), so let's go ahead and throw that out. The other is Jim Marshall, who played in 282 straight games as a defensive end from 1961-1979.
From '61-'79, however, the game wasn't as fast, physical, or dangerous. Today's players are immeasurably bigger, stronger, faster, and chemically enhanced, and they're also running around throwing more cut blocks at people's knees. Jim Marshall's mark is incredible, for sure, but I'll take 253 starts from a QB today over 282 games from a defensive end in the '60s and '70s.
For 253 games, Brett Favre might as well have taken the field wearing a sign that said, "Please, freakishly athletic and angry 300-pound men, try your hardest to hospitalize me." He's been doing it non-stop since 1992, when he stepped in and started a Week 4 game against the Steelers.
If you've got a fantasy football team, you know how big of a role injuries play in the NFL. The game is so fast and unforgiving. For a guy to make himself a target for every linebacker or defensive lineman on the field about 40 times a game, and do that 253 straight times ... it's mind-boggling.
In order to catch Favre, Peyton Manning, the next guy on the list, is going to have to play through the age 37 without missing another start. He's currently at 160. The most consecutive games any other quarterback has ever started was 116 by Ron Jaworski.