Call of Duty is hated on because they've created an atmosphere where everyone thinks they're 'great' at the game. Activision has made it just like World of Warcraft. Dumbed down and easy to play for everyone (Some people would argue that's not a bad thing). It's hated on because it's just like a dumbed down sports game.
Many of us have memories of getting face rolled in Goldeneye 007 until we learned the game and got good enough to stand on our own two feet. PC gamers know what I am talking about when we speak of a new player in Counter-Strike.
Much of this genre has never been this fast-food FPS that Call of Duty has presented.
When you add onto the fact that Call of Duty is released yearly with the most minor updates(Like many sports franchises)... (Changes in perks and new skins for the same guns) And lastly it's absurd over-whelming popularity is embarrassing. You have a recipe for people to dislike the series.
To add a real life flair to it, It just seems like this new generation of individuals (Especially in the United States) is just so engrossed with getting what they want, when they want it without having to work for it far more than previous generations behind them. It's also a generation which hasn't been taught the value of winning and losing, They've been told their special regardless. They're the most technologically advanced generation with technology to do tons of things at the palm of their cell phone yet many of them know less about the technology than youth in the 1980s.
Call of Duty is an example of where society has gone and eroded to. Easy access, Minimal challenge, Excessive hype, No one loses all the time because we're all special players.
On a side note, I really enjoyed Modern Warfare (The Original). It was different, unique, etc. After Call of Duty 5, MW2, Black OPS being pumped out like Guitar Hero expansions, I officially can't stand the series. It's ridiculous. It's the same shit re-skinned and repackaged for $60.