I own 7 retail DS games:
Guitar Hero On Tour (came with my special edition DS)
The World Ends With You (bought used, no money for SE
)
Mario & Luigi - Partners in Time
Mario Kart
Tetris
Animal Crossing (US import, loved the game)
Castlevania - Dawn of Sorrow
I also owned these games: Lost Magic, Polarium, Pac Pix, Bomberman, Meteos, Another Code, Wario Ware Touched!, Mr. Driller, YuGiOh - Nightmare Troubadour, Rub Rabbits, Nintendogs Labrador. I sold some of them even before I got my flash cart, because I didn't like them or they had no replay value.
After I got my cart I only bought Guitar Hero and TWEWY, but I plan on buying PuzzleQuest Galactrix.