My GameCube game works in another system, but not my own?
Solution 1:
Gamecubes' (and a lot of optical disc based systems) laser lose some of their potency over time. I've had this happen on a few units and there is a fairly straight forward diagnosis and fix you can try. All it is is adjusting the Potentiometer to allow more juice to the laser that reads the discs
There are numerous YouTube videos that show the entire process as well