It is baffling that Elite 1984 isn't on there. It is a pioneer of 3D graphics and open/sandbox gameplay, it paved the way for games like Wing Commander, GTA, etc and many space games after it. Hell even Sean Murray says NMS is inspired by Elite because he grew up playing as did many other developers. It was also a technological marvel for its time besides its revolutionary game design and financially one of the most successful games ever, especially for its time. I know its sequel/spin-off of Frontier: Elite II is on there but the original is way more important for what it contributed technologically and to game design.
Also I know that STALKER didn't do anything ground breaking to FPS itself but its contribution of atmosphere and horror in the FPS genre is the best I've seen, it's the only FPS game that does survival horror right and includes RPG elements and doesn't sacrafice FPS for RPG and vice versa. It's important for what it did plus its unique setting, it's a game that has never been repeated even though other games have attempted and failed. It's a game that got survival horror, atmosphere, FPS and RPG elements all rolled into one into a one of a kind experience only on PC, that's pretty important to me. If you're going to have System Shock 2 there which I love dearly as well, STALKER deserves it as well.
Also no mention of the X series... where is X3: Terran Conflict and Albion prelude or the older games? It is the biggest sandbox game in depth and mechanical complexity ever made that has contributed to gaming, it's basically a 4x game but in 3D where you are in the world, where you can build your own trade empire by amassing your own freighter fleet, building factories if you want, traders, then building a military fleet to protect your assets, engaging in wars, exterminating sectors, you can do anything. You fly the ships, you command your capital fleets in battle and in other sectors (or they work on your behalf), etc. It's a series that has heavily contributed to space games even upcoming ones, EVE Online even took inspiration from the older games. We're seeing games like Star Citizen and others using ideas from this series and has had developers reference the X series in the past.
Otherwise I agree with the list.