If influential means influencing game design / the industry, inspiring other creators by demonstrating novel ideas, I’d probably have to say Doom or Half-Life. Doom really showed what an FPS could be and kicked off such a dominant genre. Half-Life introduced immersive storytelling that greatly influenced FPS and non-FPS games.

And before AI we had “Thinking Machines”.

Perhaps we should go back to that. OpenAI et al can brand themselves “Think-Tech”