Wolfenstein 3D, Wolfenstein 3D - Spear of Destiny, Doom 1 + Doom 2. The most known.
Also:
Nightmare 3D,
Rise of the Triad,
Ken's Labyrinth (not that well known one),
Blake Stone - Aliens of Gold (good one, was almost competitior to Doom)
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Heretic
Hexen
Hexen II
Heretic II
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This 4 games above have continuing story and belong together
Dark Forces
Descent
Descent II
I guess, enough for now?
