We don't have a game that tries to talk about why games are great. The closest we have is the newly-released Evoland. It's not as overt as McCloud's book in that at no point is an author directly addressing the audience, but it's absolutely a game about games that (to an extent) could already teach people a lot about history and design techniques and feature-creep.
The conceit of Evoland is that it's a game that keeps adding more features. Initially you start as a gameboy-esque sprite-based character who can only move left, then collects the ability to move right, then up and down, then from one screen to another in a loading-scroll, then graphical quality boosts until you've gone from a simple pixelated experiment to a highly defined part-RPG-part-adventure game.
It's a love-letter to Final Fantasy and The Legend of Zelda, and it doesn't intend to be much more. It has some interesting mechanics that actually turn it from an interesting joke to a genuinely compelling game, but by largely choosing to emulate classics without much of a commentary on why it even wants to do that means it misses an opportunity to achieve something much more worthwhile.
Right now it's a game that gives you a goofy nostalgic look-back at the journey from Ye Olde Vid Game of Yesteryear and the progression to... I guess games that are even not currently being made at the moment. It's a shame that it doesn't do more, but hopefully it inspires something that does.