We can keep looking into these inane arguments of why RE4 sold in Japan but Dead Space didn't and picking apart tiny details of art, gameplay, music which end up collapsing when the argument is applied to any other game.
Or we can just accept that the Japanese development cycle over the past 20 years has resulted in a cultivated relationship with magazine publications offering weekly interviews and updates; retailers negotiating exact shipments which, unlike the west, they cannot return so have to know a good deal about what they're getting; and publishers sticking to the rhetoric "if you can't succeed at home you can't succeed anywhere", along with perhaps a bit of personal pride stake in being able to see their product go big (or bomb) around them; and a general disinterest among western publishers who do not see it as a need to succeed in Japan, unlike the reverse, instead choosing to license their game to Japanese Atlus USA-style outfits with next-to-no money, altogether culminating in a situation where by the time the Japanese consumer goes to shop to buy a game, they have no choice but to buy a Japanese game.
Or, you know, we can just go with racism and call it a day as usual.