For me personally, I enjoy Modern Warfare 2 way more than I probably should. I harp on the Call of Duty series all the time for being unoriginal, and for driving people away from more complex, tactical shooters in favour of mindless point and shoot with samey, repetitive weapons. I play a lot of ARMA, Rising Storm, Red Orchestra, Payday, and generally a lot of games that require team coordination and a high degree of strategy and situational awareness, and every now and then I just like to throw all of that out the window, set Steam to appear offline, log onto an MW2 server, and Rambo it up for a good few hours. It's an older game in the series, and there are only about 300-500 people online at any given time, but I still find it to be the only Call of Duty game I can have fun with.
So what about you guys?