ds:
- kirby canvas curse, super star ultra (obligatory to mention, these were my childhood)
- mega man star force 1 and 2 (successor to the gba battle network series)
- all the castlevania games (theyre all pretty good)
- dragon quest joker 1 and 2 (like pokemon but dragon quest)
- scribblenauts and super scribblenauts (weird puzzle games)
- custom robo (mech game for kids, but you can make your own little toy mech which is pretty cool)
3ds:
- kirby triple deluxe and planet robobot (also obligatory)
- shin megami tensei iv + apocalypse (really good and really hard rpgs)
- all the etrian odyssey games (also really good and hard rpgs)
- professor layton miracle mask and azran legacy (british)
- culdcept revolt (personal fav, mix between magic the gathering and monopoly)
- little battlers experience (another mech game for kids)
seconding starfy, that game is the shit