As far as I know, it's just a reader convenience survey.
As an example, taking a sample one from November 12th (gonintendo regularly posts them): The top is still the same as today (FF13, BH5, MGS4). Blue Dragon is #3, Twilight Princess is #6. So far, Wii Sports and Wii Play have each sold over TWICE as much as Twilight Princess in Japan, yet didn't even make the top 20 list. Blue Dragon sold even less, only 140,000 copies so far.
To sum, two games that sold over a million copies so far didn't make the list two weeks before release and the #6 game has sold 3 times the amount of #3.
It only shows what Famitsu readers want and doesn't say much about what Japanese sales will be.
The article discussing Famitsu most wanted chart for March 23-29 had Resident Evil 5 as #3. I don't know how accurate those charts are, but this would indicate strong demand for the PS3 version over the Xbox 360 one. By the time this game is released, the PS3 should have made pretty good ground catching up in North America and Europe. I would rate this one over the Xbox 360 version.
9
As an example, taking a sample one from November 12th (gonintendo regularly posts them):
The top is still the same as today (FF13, BH5, MGS4). Blue Dragon is #3, Twilight Princess is #6.
So far, Wii Sports and Wii Play have each sold over TWICE as much as Twilight Princess in Japan, yet didn't even make the top 20 list. Blue Dragon sold even less, only 140,000 copies so far.
To sum, two games that sold over a million copies so far didn't make the list two weeks before release and the #6 game has sold 3 times the amount of #3.
It only shows what Famitsu readers want and doesn't say much about what Japanese sales will be.