Mario Kart DS
Phantom Hourglass
Metroid Prime: Hunters

my fav dss games so far are Zelda Ph, Hotel Dusk Room 215, Phoenix wright series, Apollo Justice Ace Attorney and Castlevania series.

I would say:

Zelda
Pokemon (choose your gem)
The World Ends with You (crazy music)
A Harvest Moon, Rune Factory was my favorite
Final Fantasy Tactics A2
Elite Beat Agents
Mario Kart
Advance Wars (both of them)
Professor Layton

This is by no means a comprehensive list, but definitely a start

anything from this list http://www.neogaf.com/forum/showthread.php?t=222049

I personally suggest
Professor Layton and the Curios Village - awesome puzzle game, great if you like classic puzzles such as the Tower of Hanoi. It has a few extremely challenging puzzles, but that doesn't stop you from beating the game.

The Legend of Zelda: Phantom Hourglass - if you love Zelda, it is a obvious choice

Advance Wars: Days of Ruin - excellent Strategy RPG, if you like chess or other strategy games, you'll probably like this.