Beware the Madden Curse!
From wikipedia, http://en.wikipedia.org/wiki/Madden_NFL :
The "Madden Curse"
Prior to 2000, all of the Madden NFL game box covers prominently featured John Madden only. When EA started to have NFL players on the cover of the Madden NFL games, some later (half-jokingly) speculated that there was a "Madden curse": a coincidental series of misfortunes that befell the product's cover-athletes. People started noticing a pattern with St. Louis Rams' halfback Marshall Faulk from the fallout of a Super Bowl-winning season, and great season statistics earned a cover spot. The following year his stats dropped sharply compared to his prior season. Also the Atlanta Falcons' star player, quarterback Michael Vick, was injured during the 2003 preseason after posing for the cover of Madden 2004. Vick suffered a broken fibula in a preseason game against Baltimore, the day after Madden 2004 was released to retailers. The injury resulted in a painful 5-11 year for Vick's team. Although people who believe in the curse state that the featured player will wind up having a weak or injury-prone season, EA officials point out that Ray Lewis and Eddie George appeared on the covers of the 2005 and 2001 versions, respectively, and had successful seasons without injury.
The first NFL player to be on a Madden NFL cover was Barry Sanders in 1999, for Madden 2000. He shared the cover with the then-customary picture of John Madden. However, a week before training camp began in 1999, Sanders abruptly retired - ending his career and leaving the Detroit Lions without their star running back of the previous 10 years. Sanders' part in the curse is debated because he is not pictured alone on the box, and he had willingly retired.
Dorsey Levens was also featured on the 2000 cover, but that version of the game is much less common. He was cut by the Green Bay Packers in 2001, and finished his career in 2004.
Eddie George, then of the Tennessee Titans, who graced the 2001 box, was the second 'cursed' player. Although he had the best year of his career, rushing for 1,509 yards, catching 50 passes for 453 yards and scoring 16 total touchdowns, he was cursed by bobbling a pass in the playoffs. The pass was then intercepted by Baltimore Ravens linebacker Ray Lewis, who returned the ball for a touchdown. George, (up until then) known for his durability, would also get injured the following season. After regularly averaging nearly 4 yards per carry in his first five seasons and rushing for over 1,300 yards in each one, he averaged only 3 yards per carry and rushed for career lows of 939 yards and 5 touchdowns in the 2001 season. For the rest of his career, he never averaged more than 3.5 yards per carry, but did rush for over 1,000 yards twice and scored 14 touchdowns in 2002.
Former Minnesota Vikings star quarterback Daunte Culpepper appeared on the 2002 cover, and the Vikings struggled to a 4-7 record until Culpepper was shelved with a season-ending knee injury.
Running back Marshall Faulk of the St. Louis Rams, who was on the 2003 box, suffered an injury and had a bad season overall. He never broke through the 1,000 yards rushing mark for the rest of his career.
One day after Madden 2004 hit the shelves featuring Atlanta Falcons quarterback Michael Vick on the cover, Vick was injured during a preseason game, suffering a fractured right fibula. Vick played in only the last 5 regular season games, finishing with only 585 yards passing and 4 touchdowns. The Atlanta Falcons missed the playoffs and were already out of contention by the time Vick returned from his injury. They finished the season with 5 wins and 11 losses, a stark contrast to the team's 9-6-1 record the season prior.
Madden 2005 featured Ray Lewis of the Baltimore Ravens. He had an injury that kept him out of the last game of the regular season. It was also Lewis' first season without a single interception, after posting a career-high 6 the previous year. The Baltimore Ravens also failed to make the playoffs that season (2004), after winning their division the year before. Furthermore, in Week 6 the following year, Ray Lewis' season was ended by an injury. 
The Philadelphia Eagles' star quarterback Donovan McNabb was on the cover of Madden NFL 06. Prior to the 2005 season, McNabb had a highly-publicized feud with his teammate, wide receiver Terrell Owens (who was, coincidentally, the cover athlete for rival Sega Sports' ESPN NFL 2K5, though no "Curse" had been associated with that series of games and won't be, since EA purchased exclusive rights to the NFLPA, thereby eliminating any NFL-based competition). Also, in the first game of the regular season, McNabb took a hit to the chest from the helmet of Atlanta Falcons defensive tackle Chad Lavalais. After the game, it was revealed that McNabb had a 'sports hernia'  that needed surgery. Refusing to have the required season-ending surgery while the Eagles (who had made the Super Bowl the previous season) still had a chance to make the playoffs, McNabb played in discomfort and pain throughout the season. In the tenth game of the season, McNabb re-injured his groin when shoved to the ground by Dallas linebacker Bradie James while McNabb was attempting to tackle Dallas Cowboys defensive back Roy Williams, who was returning an interception for an eventual game-winning touchdown. McNabb did play the next series but was ineffective and then decided to pack it in for the rest of the season. On November 21, 2005, McNabb, on the advice of his doctors, opted to have season-ending surgery for his sports hernia; the Eagles had been eliminated from playoff contention and finished the year with a 6-10 record.  
The MVP of the 2005 NFL season was the cover athlete for Madden 07 in 2006. He broke his foot in Week 3 and will be out 2-4 weeks. At the time of the injury Alexander had only 187 rushing yards and two touchdowns on the season and has yet to rush for 100 yards in a single game. At the same point in the previous season Alexander had 257 rushing yards and five touchdowns.
Say what you want, but it's just plain freaky. As Ram fans we have felt the wrath of this curse first hand. A warning to all NFL stars: STAY AWAY FROM THE COVER OF MADDEN GAMES! That is unless you want to recieve royalty checks for the rest of your life, and take it easy spending your millions you made from being on that cover while recovering from the "cursed" injury. :)