I was trying to think of which games created certain mechanics that became popular and copied by future games in the industry.
The most famous one that comes to my mind is Assassin’s Creed, with the tower climbing for map information.
And then there was the Quake 2 engine which gave us Deus Ex, American McGee’s Alice and then (through the modified GoldSrc version) Half-Life, Counter Strike and countless others! The family tree of 3D engines is really interesting.