The holy trinity of FPS games

[Doomsday]

Doom Blood Half-Life

Alternate Dimension: TF2 Dusk Doom Eternal

I'm surprised no one has really mentioned Blood yet, I thought that was part of the trinity.

[BROS_ETT_311]

I know someone already mentioned this, but definitely: Wolf3d, Doom, and Quake. Not only was each entry a significant technological advancement for rendering graphics in its heyday, but they additionally laid the foundational game design philosophies for what would come to be know as first-person-shooters. As much as I appreciate the Build engine and all the unique scripting capabilities it could do, it was nonetheless iterative of what IDsoft had already done with their engine. Granted, yes, you could jump/crouch, look around on the vertical axis, and destroy environments within those games, but by the time Duke3d had dropped Quake was already providing a true 3d environmental gaming experience merely months later.

[CivilianM91]

Doom, Halo, Unreal Tournament

[Chezza]

Doom, Duke Nukem, Blood - if we're referring to classic FPS

 

But for me personally it's Doom, Half Life and Stalker.

[YeOldeFellerNoob]

DOOM, Quake, and Half-Life.