Unsurprisingly, looking at point differential delivers similar answers to the question, "Who was the team of the decade?" The Patriots have the best point differential for the decade (+1,106), and the best single season point differential (+315 in 2007, as far as I could tell the best of all time). The Pats only had one season with a negative point differential and that was back in 2000.
Almost impressive as the Pats are the Colts, who had an overall point differential almost as good, and also only had one negative season, 2001.
Just as unsurprisingly, the Lions are at the bottom of the list with a whopping -1,225 point differential. They are also the only team on the list without a positive season. Their best effort was in 2000, when they had an even point differential.
We've determined the teams who were best and worst, but who was the most mediocre over the past decade? The Dolphins ended up having the point differential closest to zero, with a total of plus five, but the true kings of mediocrity are the Redskins. The Skins are the only team who did not have a point differential in either direction of over 100 points and have the smallest range between their best season (+66 in 2005) and worst (-85 in 2003). As a Redskins fan, I find this stat frustratingly expected. Anyone who has followed this team over the past year has no doubt in their mind the Redskins have played the most close games in the NFL. They almost never blow anyone out and rarely get blown out themselves.
Just as the Redskins spent most of the decade on an even, slightly below average pace, the Rams were the most up and down team of the decade. In their best season (in 2001) the Rams had a point differential of +230 on the season; in their worst season (this 2009 season) the Rams got outscored by 261 points. This leaves an astounding difference of 491 points between the Rams best and worst season of the decade.