It's a bit frustrating that I find myself coming back to discuss a silly and overused piece of hyperbole like "Citizen Kane of video games", but I still think you gentlemen are misreading it. Citizen Kane isn't really remembered for being a sophisticated study of the human condition, it's remembered for pioneering cinematic techniques and using them extensively in a novel way, for exhibiting an unprecedented degree of "film-itude" that future films would mimic. From the list you mentioned, the films of Leone and Herzog are primarily about judicious and audacious exercise of style, too - elevating what is sometimes quite trashy source material into visions of the world that are unique and possible only through the medium of cinema.
A game might theoretically merit a comparison to Citizen Kane - or any of the above - if it managed to establish and popularise an uniquely "game-y" way of telling stories and conveying ideas that other games would then follow. Well, the joke is that games have been doing uniquely gamey things with stories and narratives for years, so the whole exercise is kind of pointless, right? I don't think there will ever be a game that would achieve a status comparable to Citizen Kane in games, simply because games in themselves do not, and hopefully never will, form a cohesive medium to the extent that films do. Having said that, trying to further develop the "language" of games and do more with it is far from pointless, though, and serves a greater purpose than game journalists' misplaced desire to occasionally feel like they are writing about a very serious, very highbrow medium.
