how does it not matter if it's a new franchise? Do you think Joe RPG is gonna outsell Dragon Quest? I would imagine the only reason Resistance sold is because there was nothing else to buy. Hell even Gundam (not musou, the other one) sold 130,000, and that is a god awful game.
You're also comparing a system that has sold .38 million with one that has sold .9 million. Hell, i would argue that many of those .38 million are not even Japanese. Also it is highly likely Forza will have no marketing.
currently playing: Skyward Sword, Mario Sunshine, Xenoblade Chronicles X