Bryan Burke over at NFL Stats created a chart of team performance over the last decade using yearly offensive and defensive EPA plotted against each other. This creates a chart in which being in the upper right is good and the lower left bad. So each team gets 10 plots on the chart, one per year. You'll never guess which team was consistently the best and which was the worst... well, maybe you will.

The best team, the high-and-righty we might say, is none other than the Pittsburgh Steelers. The worst team? Well, the writer didn't really say in the explanation but you are able to go down through the teams one by one. Start with the Browns and you'll see almost every point plotted in the lower left quadrant of the plot. Now go through every other team. There is no other team that is more consistently in that quadrant of the plot than the Cleveland Browns. Only Detroit even approaches the consistency of badness of the Browns.
The fact that the Browns continue to sell out while teams like the Bengals and Chargers get blacked out says something about Browns fans. What is it about the Browns that motivates such devotion?