Beyond unrealistic
Interceptions are a huge problem, players seem to instantly know exactly where a ball is going, and receivers seem content to stand there and watch the pass be picked. Players will slide, fly, literally teleport to the ball and make ridiculous interceptions, while receivers will hardly change their route at all. Especially on All-Madden, the amount of unrealistic interceptions is horrific.
Second, the AI in general is awful. Blockers will let players run right by, and plays like the HB Pass or even running with the QB are overpowered as the defense almost never reacts well. The only reason the game is harder at different difficulty levels is because the players stats literally change, not because they actually play smarter.
There are no more historic teams, franchise mode in my opinion has gotten worse, without even the option to practice with your team. Superstar is shallow as ever, and modifying sliders is required to have even a semi-realistic game.
Unfortunately, the exclusive license between the NFL and EA has been renewed until 2012 or something, so unless the developers seriously reform this game, we will probably be stuck with this same garbage every year.