1. Halo: Combat Evolved (2001)
One could make the case that the first Halo title was the first game to truly usher in drama-based, narrative-driven FPS action. Orchestral scores, massive firefights, environments that dwarfed players, alongside 3D graphics converged to form a completely defining experience. Bungie went all in with the original Xbox's launch title, introducing Master Chief as the face of next-generation gaming and creating a fully realized and addictive multiplayer component that had us schlepping consoles to friends' houses for system-link LAN parties for weeks, then months, then years on end. Need proof? Try the multitude of titles since the original game's release, and the unrelenting hype between releases as evidence of the game's long-lasting legacy that isn't going away any time soon.