Yes, it's a milked series, and yes, Ghosts sucked, but on the whole, Call of Duty games are well made, not very glitchy, and fun to play, especially with friends.
Which one has been your absolute favorite?
Mine was Black Ops. This is where Call of Duty peaks. An incredible singleplayer campaign with a mindfuck of a story, and some insanely fun missions, and the best multiplayer mode in the series, along with the best general setting... man, Black Ops was an amazing game. Pity we're never getting anything else like it ever again.