[coldpie]

Halo 2's online multiplayer introduced (or popularized?) party-based matchmaking. So instead of having to coordinate all your buddies joining the same pre-existing server, you'd join up as a party and then drop into a matchmaking queue, which would set up a game against opponents, optionally taking a skill-based ranking into account. They even did a bunch of marketing around this, since it was a new concept at the time: https://www.youtube.com/watch?v=YGSuPZVgxLg