The list to take to the store with you is here:
http://www.neogaf.com/forum/showthread.php?t=222049
An amazing list of the absolute best DS games and it is constantly updated.
Or you could look at IGN's newly released Top 25 DS games list (not as good as the above, but it includes Sapace Invaders Extreme, so I have to give it a nod as well)
http://ds.ign.com/articles/921/921522p1.html
But definitely check out the GAF list. Wow.
Wii Code 3456 7941 4060 2924