However, you should keep in mind that the Nintendo 3DS utilizes a different screen resolution than the Nintendo DS. As a result, any Nintendo DS game that you play on the 3DS might look a bit stretched-out and blurry.
Luckily, it's possible to boot your Nintendo DS games in their original resolution. Before selecting your Nintendo DS game from the bottom menu, hold either the START or SELECT button. Then tap the icon for the game cartridge. Keep holding the START or SELECT button. If your game boots at a smaller resolution than what's normal for 3DS games, that means you've done it correctly.
Now you can play your Nintendo DS games as you remember them: Crisp and clean.