"I do not think we should attribute bad software sales solely to piracy. It is true there is always the influence of piracy, but it is important for us to increase the number of our consumers who are willing to shell out their money to purchase our products. So, we do not intend to think that slower sales are solely due to piracy." - Satoru Iwata.
This coming from the most anti-piracy gaming company ever, the one who made firmware updates every three months which does nothing but block homebrew and flash cards, and the one who whined about losses over Pokemon Platinum ROM downloads, and also the one who's going all out to prevent 3DS from suffering the same fate (we all know it's not going to happen anyway).
But what Mr. Iwata said stands true though- if your game gives you value for money you would be willing to spend more for a genuine copy. If your game stinks, or people on another region of the world have no opportunity to play your game, expect them to be pirated.
Slower sales are mainly due to bad quality FIRST, then piracy.
