FPS games are all about multiplayer... so if you ask me, it's Quake. Wolf, Doom and Duke were early experiments... but Quake was far bigger on the net back in 96'. I remember.
Camperfield style games, including CoD and MoH... need to go away so the younglings can see what proper action looks like.
No taking a knee to manage your CoF, no radar, no spotting- just balls out high speed twitch that requires speed-of-thought three dimensional thinking.
...
It would make a lot of kids who thought they knew something about FPS games cry. Part of the reason slowed-down FPS ala BattleField is so popular, it's easy, anyone can play, sells more copies.