I've played them all expect Call of Duty: Modern Warfare 3. I think they haven't been good since 4. 4 had a good somewhat believable campaign and had a really fun and balanced multi-player, 64 player team death-match was a blast. WaW was mediocre, not even the zombies saved it for me. Call of Duty: Modern Warfare 2 and Black Ops were just awful, the multi-players are just a mess, and the campaigns are just crappy over the top action movie bollocks.
An Example: The No Russian level in CoD: MW2, you play as an uncover Marine CPL put there by the CIA. You follow 3 terrorist including the ringleader, whathisface, into the airport. You're armed with and M4/M203 and a M240. My first thought as the level starts up and the 3 guys open fire was why don't I just hang back put a 203 round at the feet of the 2 goons and then put a couple of rounds of M4 or M240 into the back of the ringleaders head, and double tap the buggers just to make sure. Bad guys dead, limited civilian deaths, no dead CIA agent to cause war between USA and Russia, Job done, Game Over, I Win, Right?
I think the Campaign in the Medal of Honour reboot is soo much better
OH, also MW, MW2 and MW3 = MechWarrior (1989), MechWarrior 2 (1995), and MechWarrior 3 (1998) NOT Modern Warfare