Let's have an argument. A thorny, stat-and-fact intensive, yet aesthetic argument.
I know people who can argue for hours over which NFL franchise was the best in any given decade (the 70s and the 90s pose particular problems), but ranking football teams since the AFL-NFL merger in 1970? That's an argument.
While ESPN's "formula" and arbitrary criteria avoid the problem of ranking teams and players from decades in which the game was wildly different from what it is today (how does one compare the Browns of the 1950s to the 49ers of the 1980s?), the cutoff date shorts the not quite pre-modern Packers under Vince Lombardi, who won the first two Super Bowls and a slew of championships in the 1960s, as well as the Kansas City Chiefs, a great team right up until the merger, when they promptly went to hell.
I have quibbles with the list, though it's based on a formula. Recent success aside, the Patriots don't belong in the top 10, for sustained excellence over time I'd place Miami ahead of San Francisco, and I have no idea why the Rams rank several spots ahead of the Giants. I also agree with certain controversial rankings, like placing the Minnesota Vikings, who have never won a Super Bowl, one slot ahead of my beloved Redskins, where Dan Snyder has done everything in his power to destroy the legacies of Joe Gibbs and George Allen. But it is an interesting list, and worth discussion.
The only matter beyond dispute is that Jim Brown was the greatest player of all time. Have at it if you're so inclined.