For a few years my Twilight Princess game wasn't working. I was as Wolf Link in the beginning heading in Ordon village to get the sword and shield and my game would crash and say there was a troubleshoot error. I didn't really even have scratches on the disk, and I love TP, so I was a bit worried.
We had this disk cleaner about 2 years after this and I decided to try cleaning the disk and it worked again. About 6 months later though my first Wii stopped playing any and all games, as the ball bearings in it stopped working and so I wonder if it was really the disk or if it was the wii that was slowly breaking down.
Same situation with Mario Strikers Charged, though I haven't tried seeing if it was fix due to many reasons, mostly just knowing how pissed off I'll get at the game again.