i would suggest pokemon since it is the best game that is currently out there (for any console/handheld) but you should probably buy it to support the great company
You should actually do the opposite of this post. Pokemon is and always has been as shitty RPG.
Anyways is what I do to decide games, is I look down the list, and download every game that sounds interesting, or looks interesting or that might be fun. And I just put the ones I want to try the most on there. Most of them end up sucking hard, delete those, and put a few more up. Eventually you get a solid list of games.
Although I'd probably recomend anything in Neophyte's post, WarioWare, Megaman ZX, Kirby Squeek Squad (short but fun), Mario Party... hmm.. Not sure what else I'd recomend for now.
And EvilDemon, just update you firmware. If a game doesn't work that usually fixes it.