An important personal note to the FG guys

[Sexbad]

No, Valve are known for the great quality of their games. In fact they probably have the very highest game quality. Half Life, Half Life 2, Episode 2, Counter Strike, Team Fortress and so on.
Half Life 2 is pretty much the father of all modern FPS games having introduced realistic physics, believable ragdolls and all that plus lots of neat technical stuff that ever game has had since.

So, Far Cry didn't have physics or ragdolls that owned the Source engine's weird sliding furniture or AI that owned Half-Life 2's AI that just stands there and fires at you with the occasional strafe.

Half-Life 2 had good animations that were detailed for the most part but the terrible (terrible) lighting let me down. The gameplay was nothing beyond walk, crouch, sprint, jump, shoot, and a bad driving mechanic, with the exception of the novelty of throwing boxes at enemies, which turns out to be far more damaging than multiple bullets lodged in an enemy's skull. The weapons are melee, pistol, automatic weapon, shotgun, sniper weapon, grenade, and RPG, all having existed before this game existed.

Half-Life is solid. It is immersive, but not revolutionary. Even not for 1998.

They are pioneers in nothing more than some game scripting.