Now that Halo is dead, which game deserves the title of "Halo killer"?

For those too young to remember, back when Halo was huge every gaming publication was always like "is this new shooter X going to be the Halo killer?" Every time a big multiplayer shooter was announced, there was speculation about whether it was going to be the Halo killer.

Now that Halo is dead, which game was the Halo killer?