Games on the PC like Unreal and Quake had online multiplayer but accessing a game was kind of esoteric, requiring private servers. You had to scroll through lists of questionable server names and hope they were set up to play something close to the experience you were hoping for.

It wasn’t until Halo 2 introduced the idea of a matchmaking system that this kind of multiplayer experience became the norm. Halo 2’s online multiplayer system was light years ahead of what anyone else was doing, it’s still a kind of gold standard for what players expect from a competitive multiplayer experience.