Let's see, what have I got...

*counts* 20.

Trauma Center: Under the Knife
Trauma Center: Under the Knife 2
Etrian Odyssey
Etrian Odyssey II
Rhythm Heaven
Bangai-O Spirits
Big Bang Mini
The World Ends with You
Disgaea DS
Final Fantasy III
Final Fantasy IV
Final Fantasy Tactics Advance 2
Dragon Quest IV
Mario and Luigi: Bowser's Inside Story
Elite Beat Agents
Kingdom Hearts 358/2 Days
Legend of Zelda: Phantom Hourglass
Pokémon Pearl Version
Shiren the Wanderer
Guilty Gear Dust Strikers (heh, no comment)

Probably will be added to my collection in the near future:
Pokémon SoulSilver
KORG DS-10+