>>6 Hm, you are right in that there are some fairly gruesome games here in Japan. I don't play them because I find them rather distasteful, but I know Biohazard and Silent Hill are quite popular.
Now, I am dating myself here, but I was an avid gamer when I was a teenager, and that was almost 15 years ago. My first computer was NEC PC-8001 mk II with 64KB of RAM I got in 1984, the best PC game for me is Y's II I played on my father's PC-98 in 1988, and I was fairly good at Street Fighter II that came out in 1991ish. I am not going to bother you with all the boring details which I am sure you have no idea about, but my point is that video games in Japan back then didn't contain as much violence as games today, and there are significant generational differences between today's gamers and gamers back then in terms of their mindsets and preferences.
Going back to the main topic, which is the lack of acceptance and popularity of FPS games in Japan, another explanation I could offer is that there is no gun culture here in Japan, and only the police (and mafias) have access to real firearms, which is a good thing IMHO. We do have miriota ("military otakus"), of course, but there just aren't too many of them, and they can only play with plastic toy guns.
These two factors, that is, a lack of interests in violent video games among older Japanese gamers and the absence of gun culture in Japan pretty much explain why FPS games are not as popular in Japan as in the United States. These are just my two cents on Japanese gaming culture, though. What do you think?