The oldest one I played is RTCW though

I thought of completely different games when said ‘old’

I thought you couldn’t avoid murdering seals at the beginning of the game

Aquarica by Benoit Sokal

Overlord 2 lol

From what I’ve read about this, the companies (like Nintendo) rather use patents for defensive purposes (for example, patenting some new game mechanic while the game itself is still in developement in order to prevent rivals from implementing that mechanic in their products).
However, it is sometimes crazy to see what mechanic get patented. I believe I’ve seen a patent for player object being colored while a wall is overlapping it, so that the player could see it through a wall. That was from CAPCOM or Nintendo I guess