In all seriousness, blurt out some landmark games. They must fit certain criteria though. Technological/gameplay innovation, emotional or intellectual meaning and aesthetic appeal. Citizen Kane is considered the greatest because it was the first to do so many things, many of which it pioneered are commonplace now. Which games could realistically carry the torch?
Doom
Red Dead Redemption
Minecraft
Portal
Heavy Rain
Walking Dead
Braid
I'm on my phone at work so I don't really have the time to go into details about those games. Hopefully you've played them to understand the criteria I laid out.
Or just name the game which would have enraged William Randolph Hearst.
To me there are two different facets of how this could be applied, but they are quit varied with each other. Something could be "The Citizen Kane game of video games" because of the groundbreaking technological aspects that either hadn't been done before or weren't thought of being applied in the way they were in the game. I think that is somewhat valid, but also a little off the mark when it's brought up.
What most people think of, or at least what I think of most prominently, when they say that something could the "Citizen Kane" of something is that it was the first or maybe one of the first and best examples of how that subject medium could legitimately be seen as an art form and not just as a vehicle for entertainment. In that aspect it would be the games that if somebody came up to me and wanted me to give them an example of how a video game is just as legitimate form of art as other classical things. It's just so far from mindless entertainment at that point, and can carry on something at a whole another emotional level.
The technological innovations also happen all the time in video games unlike other media, even movies, thus greatly reducing their importance as groundbreaking in the medium only a few exceptions for the truly extraordinary breakthroughs. At the very least in my mind the technological improvements have to involve something than just more powerful special effects, better graphics, or being able to do more flashy moves. It has to engage the player in a more important way.
With those two criteria in mind, but giving more importance to the second, here would be my choices off the top of my head (I always forget some deserving ones.) A game also doesn't necessarily have to have a astoundingly good plot to it, but for this most of the list they are very strong in that aspect.
At the very top: Planescape Torment (and I'm not even giving it bonus points with how like Citizen Kane it was underrated and people started only appreciating the way they did some time after it came out and it wasn't a hit in sales numbers.)
At the next tier just under it: Xenogears, the first Bioshock, Chorno Trigger, Fallout 1 and 2, Baldur's Gate 2 (if Torment is the Citizen Kane of video games these then can maybe be considered the Casablanca, Gone With the Wind, Godfather and Star Wars of video games)
The third tier: Metal Gear Solid, Knights of the Old Republic 1 and 2, Luffia 2
Final tier being worthy to be in the category: Legend of Zelda: Ocarina of Time, Final Fantasy VII, Final Fantasy VI, Uncharted 2, Batman Arkham City, Heavy Rain, Red Dead Redemption
A game like Doom might have been fun back in the day, it was technologically innovative at the time, and it might be remembered for some time to come, but few people are going to hold it up as art. At least not like other games. The same can be said of games like the old Mario and Castlevania games. I would put the best Grand Theft Autos in here as well, even if later technology did give them the ability to tack on a cohesive plot to a game like that.
Even most great games that come out now would struggle to make it into my forth tier. Bioshock Infinite was hurt by it’s too bitter bittersweet ending and that it wasn’t as good as the original Bioshock. Something like Walking Dead just was overrated IMO, and I don’t see the hyped Last of Us going to the top of the list even if it might be good. Mass effect 1 and 2 where alright, but nothing special plot wise and the series, considering fair or not they are all linked as a trilogy, was ruined by one of the worst ending in video game history.
Even some classic games that might have been good missed out. One of the big ones that comes to mind is Vagrant Story. Something that seemed awesome, but was totally ruined by completely extraneous and cumbersome mechanics of the equipment, fighting, and magic in the game.
Looking at my list I noticed that while it has a good mix of classic and new, and is a mix of Western and Japanese games it is pretty RPG heavy, but then again I think that’s because RPGs (non-MMOs anyhow) are a superior story telling medium than the other types of games. Almost nobody is going to care about or remember good shooters of this day in the future, and if they do it will be because of the players and friends they found online because of it and not the game itself, the same with MMOs. They have a lot of mindless fun, but that’s the problem. It’s mindless.
There are also probably a number of games that deserve to be on my list that aren't simply because I haven't had the ability to play them yet.