I've always liked the Madden series. There's not really much reason to buy it every single year, but I do pick up a copy every 2-3 years, depending on how things look. It's just good, clean, over-the-top fun to give the computer team a good smashing. I always have a good time making an insane created team and trying to run the score as high as possible, too.
Plus, it's kind of a nice at-home multiplayer game. A lot of games don't really lend themselves well to same-system multiplayer, as split-screens tend to suck a lot. Football, though, works pretty well.
It's also funny, because each version has a few big bugs in it. They always get fixed in the next game, but then some other big bugs come out. It's kind of a funny cycle, and it usually creates some added amusement.
Really, if EA put out a Fight Night game every other year, I'd probably buy those interspersed with a Madden game in the gaps. It'd work well.