At this point, I don't think I'm allowed to badmouth Activision/Bobby Kotick anymore, considering I own every mainstream Call of Duty game from the first to Black Ops II on one platform or another (mostly PC even though they clearly hate me for that).
First experience with the series was a store demo of Call of Duty 2 for 360 in 2005, then playing brother's copy of the first one two years later; beat the American campaign and two British missions before infinitely-respawning Germans in a dam proved too difficult. Got into the series myself with Modern Warfare 2 during its free MP weekends in 2010, bought it and Call of Duty 4 first chances I got, along with Black Ops the month of release for my birthday. Multiplayer proved extremely fun at first, but since then not so much - 90% of the players in CoD4 and MW2 cheat, and BO servers are almost exclusively 24/7 Nuketown. Eventually bought most of the WW2 games; first two games are alright, but United Offensive keeps killing me in cheap ways and World at War's multiplayer is terrible.