I guess this is the right place to post this.
Sales for Pokemon Black/White have been announced,
Enterbrain has them at 2,637,285 units, while
Media Crate says 2,557,779 units. These numbers are just for 2 days.
This makes Pokemon Black/White have the biggest opening in Japan.
Here are first week numbers of past games for comparison, numbers from Enterbrain.
[PS1] Final Fantasy VIII (Square) - 2.504.044
[NDS] Dragon Quest IX: Sentinels of the Starry Skies (Square Enix) - 2.343.440
[PS2] Dragon Quest VIII: Journey of the Cursed King (Square Enix) - 2.236.881
[PS1] Final Fantasy VII (Square) - 2.034.879
[PS1] Final Fantasy IX (Square) - 1.954.421
[NGB] Pokemon Red / Green / Blue (Nintendo) - 140.074
[NGB] Pokemon Yellow (Nintendo) - 851.091
[NGB] Pokemon Gold / Silver (Nintendo) - 1.425.768
[NGB] Pokemon Crystal (Nintendo) - 707.580
[GBA] Pokemon Ruby / Sapphire (Pokemon Co.) - 1.245.003
[GBA] Pokemon Fire Red / Leaf Green (Pokemon Co.) - 955.337
[GBA] Pokemon Emerald (Pokemon Co.) - 643.987
[NDS] Pokemon Diamond / Pearl (Pokemon Co.) - 1.586.360
[NDS] Pokemon Platinum (Pokemon Co.) - 967.675
[NDS] Pokemon Heart Gold / Soul Silver (Pokemon Co.) - 1.408.980
[NDS] Pokemon Black / White (Pokemon Co.) - 2.637.285