Madden games are just roster updates every year with a tweak here and there, some people will play anything in front of their face (plus NFL Football is popular). If not for having the NFL license and pretty much being the only thing in town, what other football game can you play? Still bland football at it's blandest.
CoD games are like Madden games, minor tweaks and new maps, but unlike Madden aren't the only FPS games in town. But again some people will play anything. Fighting games were once the rage and everyone had to have a fighting game on a system, and in time only a certain few fighters would stand up to time itself. In time the FPS genre will do the same, but for now they are like the plague. I did try a CoD game awhile back, didn't like it one bit, you couldn't sneak up on the enemy AI. And even if you were running around, if you missed the enemy, they'd kill you in one shot, even if you moved around. Also ducking to heal from gunshot wounds and refreshing within 5 seconds, long gone are the days where you had to find healthpacks to actually survive.