Assuming that "masterpiece" refers to the quality and impact the games had in their time (not how well they aged) some of my picks would be:
Baldur's Gate 2 + ToB
Star Wars: KotoR
Morrowind
Read Dead Redemption 2
The Witcher 3
The Last of Us 1+2
God of War
Shadow of the Colossus
The Legend of Zelda: BOTW
Mass Effect 1+2
Disco Elysium
Half Life 2
BioShock 1
Diablo 2
Fallout 2
I don't know how objective this list is. Some picks are definitely subjective and fit more in a "flawed masterpiece" category of games that had a large impact on how I perceived games but that may not be so widely acclaimed as some others on this list.
God of War has two big strengths that make it a great game in my opinion. The first is the story with its great characters, presentation, and voice acting. The second is the overall "feel" of the game, which can be a bit "game-y" at times but is really tight overall with only a handful of core mechanics that are exceptionally well implemented.