Ignore the DS Zelda games. You want a good portable Zelda? The last one of those was released in 2005. Moving on.
Going to echo Thunk on the Dragon Quest recommendation. I forget if you're an RPG guy, but if you are, then either of those titles is a must. Personal favorite's Hand of the Heavenly Bride, but Chapters of the Chosen is similarly awesome.
Kirby: Superstar Ultra. Remake of Superstar with added a bunch of added shit. Impossible not to like. (Unless you hate rehashes).
Metroid Prime: Hunters. Modestly enjoyable single-player mode, good graphics. Multi-player's a great time sink.
Nanostray. Addictive as fuck top-down shooter.
You don't have Super Mario 64 DS? What the fuck.
TL;DR, get a flashcart, play DS, GBA and GBC games on one cartridge.