GC should stay, wipe the other scores periodically. Use the factory default for score resets or decide a # of games that seems reasonable for you. It fosters competition, it levels things out for new and lesser skilled players, and it brings in more money for the operator.
For the most part I leave my games at the factory setting for resetting the high scores. There are a few games where the number seems really low or really high, so I tweak it to get come consistency between the games.