What has been interesting is the lack of comparison between Microsoft 360's stand alone shooter, Halo 3, and Sony's stand alone shooter, Killzone 2. what makes the Japanese market interesting is that the PS3 has, for the most part, been out selling the 360 continuously, however when i looked at the sales figures, it quickly became quite clear that despite the ps3 selling more consoles, Halo 3 actually performed better in it's first week.
first week sales figures for Halo 3 were around 60,000 ,at this time sales of the Xbox 360 had only hit around 1,008,683  . day 1 sales for Halo 3 were around 45,000 
first week sales figures for Killzone 2 were 42,660  at this point, sales of the PS3 were around 3,161,440  . day 1 sales for Killzone 2 were around 20,000 
trying to think of an explanation for such disparity between them is not easy. one easy idea is that the Halo franchise is a tried and tested series, whereas Killzone on the PS2 was not released in Japan making Killzone 2, for many, the first game in the series that they have played.