Andriasang reports the newest Enterbrain/Famitsu numbers from Japan:
[Pokemon Black & White 2] sold 1,618,621 in its first week of sales. As the game was released on a Saturday, the "first week" includes just two days...
The fastest selling DS game is, of course, the original Black & White, which pushed 2,637,285 units in its first week in September 2010. That release also covered just two days.
Even with a huge 39% decrease in sales (equalling over 1 million units) from the previous version, Pokémon is still breaking records. This makes it the third best start on DS and the first million seller of the year in Japan. I can't help but wonder how much better it would have done had it been a ground-up 3DS game.