Meta RPG? Game within a game?
It’s not quite the same thing, but right now in a game I’m playing in, one adventure is about playing the game How to Host a Murder within the broader context of a GURPS Fantasy RPG. The game-within-a-game is only the focus of one thread, not the game as a whole, but it's quite interesting.
The webcomic Goblins is in part about a group of people playing PCs in a D&D game, but the meta-game aspect isn’t used as much as it once was (characters know they’re being played by players, one PC prays to the DM, another group of characters dies and comes back as new characters and knows what’s happened).