Wowww... 1 or 2 games? I can't narrow it down... I'll just list my absolute favorite DS games, you can narrow it down from there.
Advance Wars: Days of Ruin
Castlevania: Portrait of Ruin
Elite Beat Agents
Mario Kart DS
Ninja Gaiden DS
Phoenix Wright: Ace Attorney Series + Apollo Justice
Picross DS
Pokemon Diamond or Pearl
Yoshi's Island DS
And yes, I'm aware of the fact that I did not list Phantom Hourglass or NEW Super Mario Bros. Ninja Gaiden is similar, and better, than the former. The same applies with Yoshi's Island and NSMB.
Well, what kind of games are you interested in? Like... what genres?
Edit - Castlevania is a 2D action sidescroller. Nowadays, it's a little anime inspired, which makes the artwork a little less impressive, but the gameplay keeps improving with each installment.
Ninja Gaiden DS is around 8 hours long... it's longer than the NES Gaidens, but the goal is the same; to offer a short, fun, and replayable experience.
woooahhhhh giant bump
be sure to check when a thread was last posted in when you reply. this one is from march, so he's probably figured out what to get by now.
just something to note in the future.