For me it's World at war. Awesome campaign, multiplayer and the introduction to zombies. I remember after you beat the campaign, you are put in the zombies mode. But yeah it was dark and the most brutal call of duty ww2 game and best call of duty game i ever played
Best extra game modes (Zombies, extinction and survival)
No strafing or slide canceling back then
As much as most players hate Ghosts, it was the last Call of Duty game before the franchise got ruined by turning into games of who can shake the screen better with strafe and slide canceling.