I disagree with the 2D Boy man, i don't believe we will see a masterpiece of gaming just because you throw millions or billions of dollars after designers, i highly doubt that the things he considers master pieces had Avatar or Starcraft 2 like budgets. On that note i dont believe that there is masterpieces at all mostly because by the very definition of the word masterpiece is something every person should make sure to be critical about which is critical acclaim, which more or less means that someone else is saying this is a masterpiece and you should accept that because i know what a masterpiece is (possible thats not entirely head on but i may have looked up a wrong definition of the word then).
Point being that "masterpiece" is in the eye of the beholder as said above.
In my eyes and probably a lot of other gamers Portal could be one such game, its very critical acclaimed and we've all heard a "the cake is a lie" reference outside of the game by now. But believe it or not there are also people who don't like Portal, or haven't even seen or heard of it yet. On that note, maybe its something everyone should know, like the Mona Lisa painting(possibly a Masterpiece, although i've seen more interesting art in a 5th grade special kids class) then World of Warcraft comes to mind, not that everyone likes it or it being as critically acclaimed as other games but maybe besides pacman, tetris and mario its one of the few games that most people in world have heard,seen, read or even played.
All in all, do we need a masterpiece of gaming? What would be the point, what is really the point of calling anything a masterpiece of the world? Let masterpiece be the original intent, a designers best product, then sure i can agree that some tv shows, movies, music and art are masterpieces of that designer, but certainly it wouldn't be the masterpiece in everyones mind. Although could you live with the thought that even Uwe Boll would have a masterpiece (possibly the movie of his that is the least amount of bad) on second thought, lets just drop the word masterpiece completely, stick to Classic.