I recently got a smartphone and play some games on it, and playing games that traditionally use the d-pad and buttons (namely the shoulder buttons) feels really awkward and imprecise. Well mostly platformers feel that way, RPGs are awesome-sauce in that I can progress through the game faster because I can bring it with me everywhere. I could go and buy a console controller to connect to it, but then I would have to lug that around everywhere too.
I think the Nintendo 2DS has a market for it, but long-term I don't get it (as the price of the 3DS goes down or people are still willing to wait to get a 3DS, the 2DS is less appealing). But yeah, as Kleaver said, it's mostly aimed towards selling Pokémon X and Y. And if someone buys it to play Pokemon, they'll probably buy other Nintendo titles to play on the system.