From the moment the first Xbox was unveiled to the world, Halo has stood right alongside it. Originally conceived as an Apple Mac exclusive before Microsoft bought it, Halo: Combat Evolved was the original Xbox's killer app, possibly more so than any other launch game in existence. Halo made people buy an Xbox over a PlayStation 2 or GameCube, and that's remained largely the same for the last few decades. Though Halo isn't the only reason people bought an Xbox 360, Xbox One, or Xbox Series X, it's a big factor, but unfortunately that's starting to change.