I still remember people saying here that Wii would outsell the PS3 the week after RE5 was released, when in reality the PS3 would outsell the Wii for about 2 months (till may if remember correctly). Hell, even the Japan preview was the whole time wrong during those months. It was pure wishfull thinking from the staff.
VGChartz does a great job giving us numbers, but it's pretty obvious which colours they support.
In the end Japan is pretty much unpredictable and people just hope that game 'x' gives console 'a' the necessary boost too outsell console 'b'.