Doom is Alpha my friend. Quake improved upon it. If you want to get technical, Wolf 3-D is Alpha.
Half Life would not be popular without Counter Strike. Counter Strike is one million times the game Half Life is...sorry...it's the truth.
Edit: If you wish to witness gaming history....play Doom. It is antiquated, but you will see where FPS began. If you have the patience, play Wolfenstien 3-D the birth of FPS.
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