I've seen this question asked many times and quite often it even gets people calling the op an idiot as if no one would ever possibly want a DS emulator.
Personally, I don't see why, unless there ARE serious hardware limitations, no one has done it. I don't own a DS as I would never be in a position where I'd have time/want to play it. If I'm at home I'd be playing a console, and when I'm commuting someplace I'm driving. But i always read about amazing games coming out for the DS. (ala: scribblenauts). I've never played a DS outside of an emulated enviornment (pc), but I don't see how the wiimote pointer couldn't substitute as a stylus just fine.
Don't get me wrong, I remember buying our first NES console when I was a wee lad. I love me some old school games. But i'm sorry, the random 50 really obscure emulators for old old old ass architecture all put together x5000 wouldn't have even a fraction of the quality games even a crappy DS emulator could run.
Guess I'm all saying is, ya Dig Dug was fun in the 80s, but i'd rather be able to play Bowser's Inside Story. Yaknow?