Black Ops 3 is arguably the longest Call of Duty game. Most people report finishing the main story in about nine hours, which is certainly a respectable amount of time for a first-person shooter that releases just about annually.

1 Call Of Duty: World At War\n\n It's difficult to imagine a Call of Duty game being harder than Call of Duty: World at War. This game has everything all the other games had, times ten. Every map is overflowing with enemy troops. Grenades are being thrown at players from every given angle.