I'm surprised that there have been so few games that have taken the mickey out of RPGs / Fairy-Tales, I reckon that it would be possible to do this like Shrek, and mix up all the different expected elements, so you could have Rapunzel's hair as an item to get out of a locked tower, you would rescue princesses to (hopefully) get their hand in marriage, but find out that you were being double-crossed by the King's advisor etc.

I think that it would be better to poke gentle fun at RPG cliches by implementing them in terms of (fairy-tale cliches), you must get the magic sword from the bottom of the well! (fetch quest), rather than explicitly poking fun at the RPG-genre because this would draw too much attention to the fact that the game was guilty of RPG cliches and standard RPG problems. If you see what I mean? anyway, games themselves aren't that funny, but fairy-tales could be?

Games are a ripe target for satire, especially the entrenched design mechanics of RPG's. A lot of independent games, stuff made in RPG Maker and ZZT and Megazeux and stuff, base their entire plot on satirizing gaming cliches.

The good old King Quest games were full of fairy tales cliche and references to popular tales and stories.

The first monkey island was a parody of the "Treasure Island" book

You'll find a lot of examples if you look into oldies.

A lot of earlier Final Fantasy games had fairytale cliches in them, such as villains turning your characters to a frog and the need for a "Princess Kiss," I think it was called, to heal them. I do believe there are more, but I can't remember them.