Lately when friends ask my advice about which DS, I suggest getting an iPod Touch instead unless they're really dying to have Nintendo property games (Mario). It does more than just games, no cartridges to lose, and the kids will want an iPod soon anyways.
Even the equivalent games are cheaper. LEGO Harry Potter is $4.99 on iOS vs. $14.99-19.99 on the DS. Sims 3 is $6.99 on iOS vs. $27.99 on the DS.
Correct me if I'm wrong, but I was under the impression that when most people think of a DS, or any other Nintendo product, the Nintendo properties are the first thing on their minds. If you are getting a DS you probably want to play Mario, Zelda, Pokemon, or Metroid. If those do not interest you, then you are still more likely to be interested in some sort of JRPG or maybe a fighting game.
I am a gamer, and I was not even aware that there was any sort of market for LEGO Harry Potter or Sims 3 on a DS. In this case I think the stats support my view: http://www.gamestats.com/index/gpm/nintendo-ds.html
You may note there are only four non-Nintendo properties in the top 20 popular games, and of them only one (GTA) has a native iOS port, while one more (FF6) could technically run on a SNES emulator. I hope no one asking you for game platform advice was hoping to play any of the most popular portable games of the day.
Even the equivalent games are cheaper. LEGO Harry Potter is $4.99 on iOS vs. $14.99-19.99 on the DS. Sims 3 is $6.99 on iOS vs. $27.99 on the DS.