I just got the sales figures for the 1st generation of Pokemon Mystery Dungeon.
Pokemon Mystery Dungeon-Red Rescue Team (GBA) 2.06 million units worldwide
Pokemon Mystery Dungeon-Blue Rescue Team (NDS) 3.08 million units worldwide
So, the combined total is 5.14 million units worldwide.
I think the sales, in general, are not too bad.
I think there is a chance that the 2nd generation itself will hit a combined total of 10 million units worldwide.