From my favourites I would narrow it down to:
Advance Wars: Dual Strike
(missed some strategy console games during my PC years, Advance Wars is the main reason why I got the DSlite)
Picross 3D
(After Picross DS, decided to try the 3D version and it's even more addicting)
Professor Layton and the Curious Village
(Nice blend of story and puzzles, could've picked one of the Phoenix Wright's games - but they are missing those puzzles that I like)