What are some games that you can think of that are ruined by their difficulty. It can be that the games are either too hard, or too easy.
I can't really think of any good examples, but the closest thing I can think of would be Etrian Odyssey for the DS. It was a game that I enjoyed playing, but the endless grinding to level up made me quit the game pretty early on. I never played another Etrian Odyssey game after that.
I also found the first 2 God of War games and the 2 PSP God of War games to be a bit too easy on the default difficulty settings. I know you can play them on harder difficulty modes, but I never got around to doing that. I don't think it ruined the games, I still had a lot of fun playing them, but I felt kind of overpowered when fighting most of the enemies.
That's all I can think of for now.