I wouldn't bother arguing against the PS2 dominance, the system had everything going for it.
Still, with more Japanese support arriving on the Wii, it will easily be the top seller for Japanese games (actually, it already is, by a large margin). Iwata also came out and pretty much said they're going to help advertise DQX (which is basically Japanese games in general) - that can only be a good thing for KH3.
Anyway, I'd like to point out the obvious reason KH does so well in America: Disney characters. KH1 is the best selling console RPG in America to date, and there's simply no other explaination as to how it could outsell everything before it (and so disproportionately compared to other regions). Its exceptional graphics had little to do with its huge success.
