Age of Empires 2 /w The Conquers expansion pack.

Roller Coaster Tycoon 1. (2 was weaker without OpenRCT2, the real masterpiece, but idk if unfinished projects should count or not)

Quake 3 Arena, Unreal Tournament 1999 GOTY, Worms Armageddon, SimCity 3000 Unlimited, Forza Horizon 2 / Motorsport 3, Need for Speed Underground 1, Clonk! Rage, Metal Gear Solid 1/2/3, Ace Combat 4, Okami, Tokyo Jungle, Zelda BOTW, Mario Odyssey, Sven Co-Op, Killing Floor 1, Final Fantasy 7, LISA: The Painful, Everhood 1, Deus Ex 1, Left 4 Dead 1/2, Portal 2, Battlefield Bad Company 2…

I could go on and on.