All the way back in 2001, the first Halo hit store shelves, and became an overnight sensation. A Sci-Fi first-person shooter like nothing gamers had seen on consoles before, Halo garnered an immediate fan-base thanks to its smooth controls, open-ended gameplay, and its surprisingly deep cinematic narrative. While it was clear Bungie had a good idea of Halo's universe going into that first game, there's no way the developer could have known where the series would end up two decades later.