It really depends on the Pokemon you breed. If you breed, say a Japanese Mienshao with an English Ditto on an English game, the chance is 4/8192 for a Shiny (not gonna do the simplifying, do it yourself). If you breed, for example, a Japanese Mienshao with a French Ditto (not sure if they make French games, but bear with me) on an English game, then the chance for a Shiny is 8/8192. Just to clear a few things up.