Excellent point! The Brain Age, Nintendogs, and Cooking Mama type games are what catapulted the DS to that insanely high lifetime sales figure. Sure the Pokemons, Marios, etc; assisted in that but a huge chunk of DS core demo moved on to Angry Birds, Candy Crush, Pet Rescue, Bakery Story etc;
Which is why I always feel it's a little unfair to compare the DS and 3DS sales figures. 3DS sales figures arent too far off GBA and hasn't had the luxury of more than a decade on the market with a phenomenon (Pokemon) occur deep into its life cycle to help catapult sales like the GB.
The DS was once in a lifetime console for Nintendo I believe. It was ahead of his time, popularized touch screen gaming had a lot of innovative and simple games that are now on mobile.3DS is going to end with a honourable score , competing with smartphone and much better but much more expansive games. I do hope Nintendo continue to support the 3DS 1 or 2 more years until they release a successor. There are still a market for pur handheld.
The 3D did not help the 3DS, let's be honest. And Gunpei Yokoi did not leave because of the Virtual boy failure.