American McGee's Grimm: Iron John
tells the Brothers Grimm fairytale of the same name. That, except for the fact that it is written in a confusing, nonsensical style. If you jump straight into the game, you'll discover that you're playing as a little guy that kind of looks like a pirate. You're here to corrupt a happy fairytale world and turn everything into a dark, disgusting mess. But if you hadn't watched the story intro, you'd have absolutely no idea what the world was about. Of course, if you're familiar with the fairytale, you'd have some idea, but otherwise it's a disjointed and confusing mess.
Iron John was originally a tale about a prince who befriends a "wild" man. The man was described as having skin like iron, hence the name, but American McGee's Grimm takes this a step further and makes Iron John into an iron robot. The game walks through the major parts of the story where the young prince plays in Iron John's well, fights in a war, and marries the princess in the end, but it really doesn't make it into an interesting retelling.
Even after you make yourself familiar with the Iron John tale, it's still difficult to get into this game. Grimm is going around and subverting all the happy bright things in the fairytale world, but to what end isn't exactly clear. It might be interesting if you were actually changing the fairytale into something different, but you're really just running around peeing on stuff and turning the grass black. That may be reason enough for some people, but it's as if the brainstorming for the game stopped at this point.
That brings up another point. The Grimm fairytales weren't originally sugar-coated happy tales anyway. Maybe the creators were thinking of Disney when they came up with the idea. Either way, even if you accept the sweet, sugary version of the tale, there doesn't seem to be much reward or motivation to ruin it. Grimm just wants to ruin it because he wants to.