4) Call of Duty: Black Ops II (2012)
With the last few entries embracing futuristic tech and shaking up multiplayer with jetpacks and other augmentations, Black Ops II still stands as the last best example of the series' boots-on-the-ground online action. Good thing it's backwards compatible on Xbox One now.
The Pick 10 multiplayer loadout system was a heavily tweakable delight, and the online shootouts still hold up today. Black Ops II is also noteworthy for offering branching narrative paths in the campaign mode, along with missions split between the Cold War and the future.
3) Call of Duty: Black Ops (2010)
Black Ops II has the more enduring multiplayer mode, as mentioned above, but the original Black Ops had excellent online play for its time – and a much more memorable campaign mode. It's one of the best in the entire series.
Spanning events from Vietnam and the Cold War, Black Ops offers historical action with plenty of edge and intensity, along with a storyline that gets pretty surreal as it goes. Black Ops might have the best complete package of the series, with excellent campaign, multiplayer, and Zombies alike.
2) Call of Duty 2 (2005)
Call of Duty 2 blew some minds when it hit PC and Xbox 360 in 2015, with dazzling graphics and realism despite mining familiar World War II terrain. It established Call of Duty as the premier war series in a way that its predecessor didn't, and although the respectful, historically-accurate tone is way different than what followed in the series, it was brilliant for its time.
Even after all this time, it remains one of the absolute best World War II games, and a high bar for Call of Duty: WWII to hit – we still remember that utter feeling of awe encountering it for the first time. And while multiplayer wasn't nearly as fleshed out as it is today with killstreaks and the like, it was still a blast.
1) Call of Duty 4: Modern Warfare (2007)
Was there really any doubt? Modern Warfare is one of the most influential shooters of the last decade, pushing the military side of the genre away from historical recreations and towards gritty, gung-ho storytelling of near-future terrorist hunts.
From the opening tanker infiltration and escape to "All Ghillied Up" and the nuke, Modern Warfare remains consistently tense, surprising, and unforgettable. And this is where the series found its multiplayer footing with player customisation, frequent unlocks, killstreaks, and plenty more defining features that pulled you in and gave you reason to keep coming back.
It's been a decade since the original release, but last year's Modern Warfare Remastered is the definitive way to experience it now. In fact, it's the best Call of Duty release in at least a few years.