Plus the fact that everybody and their dogs have two per person already. In my opinion, it's quality over quantity. The library of iOS games is absolutely immense, with more than a few worthy titles, but it goes without saying that games developed for the DS are almost always of higher quality, hence the $30 price tag (generally) per game. Definitely looking forward to the 3DS release, and hope that more than a few games from the huge and awesome library they announced last E3 are available on or near the device's release date.
Not to drag this out, but I was talking with a buddy of mine last night who is a fanatical DS user, so much to to the point that he recently started his own 3DS blog. The good news, he understands both point of views and in our discussion he committed to me that he would give me a rebuttal in writing, its an interesting read and I thought you guys might be interested: http://www.my3dsnews.com/2010/07/28/nintendo-vs-apple-in-defense-of-nintendo/