Actually PS3 and 360 sales in the US territories are less than 2 to 1, its is about 21.8 million to 12.8 million. At least so says VG Charts which is fairly accurate overall. The US and overseas market for FF is actually better in grand totals than Japan, DQ is actually the one that is almost only popular in Japan and nearly unknown anywhere else. So the sales here stand to mean a lot, but overall I don't really think the availability on the 360 is going to be mean a lot. What it means more than anything else is that the people that were planning on buying a PS3 to play the game will be playing it on the 360 instead. Being on the 360 itself is not going to be providing a great sales boosts that SE would never have seen if they only released on PS3.

RPG sales in general are pretty finite and don't tend to grow beyond their core group. FF has longer legs than other RPGs because of name brand and so they grab up a larger part of that finite group, but in general they don't push beyond those pre-existing barriers. And I don't think the commercial is helping them push out of the box that they're already stuck it. I suspect that anyone owning both consoles will be playing it on the PS3 and anyone limited to one will be playing it on their current console. Question is how many RPG players own only a 360 currently. FF sales will be a good measure of that I think.