I can't get upset at Activision about CoD. They're sitting on a gold mine, and people keep lining up to throw money at them. Why would they risk losing those people (and their money) with massive iterations each year?
If anything, I think I'm more disheartened at the amount of people who continually go out an buy games like CoD and Madden, complain about how they haven't improved enough, and buy it again the next year.