– Front Mission The 1st (NDS, Square Enix): 17,715 units sold
Release: 03.22.07

– Pokemon Diamond & Pearl (NDS, Nintendo): 4,949,861 units sold
Release: 09.28.06

– Dragon Quest Monsters Joker (NDS, Square Enix): 1,288,314 units sold
Release: 12.28.06

– Seiken Densetsu: Heroes of Mana (NDS, Square Enix): 38,436 units sold.
Release: 03.08.07

I think Pokemon will have very similar success in the US/Europe.

Source: Gamefront