By which you mean? Do you mean a 'sandbox' game such as an open-world game (such as the Grand Thefy Auto series)? If so, such a game is beyond the scope of such a limited browser as the DSi's and likely the 3DS'. Now, maybe a more condensed, 2D one could work, but considering HullBreach is working on the long awaited "The Mystical Journey" MMORPG, as well as several other site updates, I doubt he'd be able to take on a project as arduous as this anytime soon.
It's my job to help the next generation, and set a good example for them. And for that I'll gladly lay down my life.
I think he means something along the lines of Minecraft or Terraria. Again, expansive games are difficult to create and maintain on such small-scale browsers.