The New York Times published an interesting study this week about how real life events in the NFL affected which 
teams players of Madden NFL 11 would play online with in a given week. They charted how often a team was used on a weekly basis and noted how a teams' usage would often reflect how its real life fortunes were going. For instance, the week Michael Vick accounted for 6 TDs against the Redskins, the Eagles accounted for a huge percentage of online games. The same thing happened the week the Vikings traded for Randy Moss. Of course, real life didn't imitate online life that time... Obviously, in the week before the Superbowl the two most popular teams used by Madden players were the Packers and Steelers.
The Eagles were by far the most popular team over the course of the season, accounting for 8% of all Madden games played online. The obvious reason is resurgence of Michael Vick. As those of us who played Madden during his heyday with the Falcons, Madden players LOVE to use Michael Vick online. Back then, he created such an imbalance in the game, it was almost like a cheat to use the Falcons. I remember I would back out of games before they started if I saw my opponent was using Vick. The game is a bit more balanced now, but it's still pretty easy to scramble for a first down with Vick whenever you need it.