I'm getting a DS Lite soon......

final fantasy 3

new super mario bros

elite beat agents

jump ultimate stars [only import from ***] 

metroid prime hunters 

castlevainia portrait of ruin

pokemon diamond or peral.

mario kart

phoenix write 1,2,3when its out and ,4 or u can import 3,4 or just wait.

Some of the game I like are:

Advance Wars: Dual Strike

Castlevania: Portrait of Ruin

Metroid Prime: Hunters

Pokemon Pearl/Diamond

Lunar Knights

 Jump! ultimate Stars (Japanese only, got mine from www.play-asia.com)

see http://www.metacritic.com/games/ds/scores/ for DS games ranked by average review score

POkemon, ummm Pheonix wright if you like murder and solving cases, mario kart if you like online gaming, harvest moon serious if you like farming, and so on.....

Mario Kart for racing

NSMB or Mario vs DK 2, March of the Minis, Yoshi Island 2 are all great for platform type games

For puzzles well, Honeycomb Beat/Tetris/Magnetica(puzzle loop in the uk)/Puzzle Quest Challenge of the Warlords

Or there is Big Brain Academy or Brain Age Training

All of the above are great games, just depends what Genre you like

Most Haves:
- Mario Kart DS
- New Super Mario Bros
- Osu! Tatakae! Ouendan (Import. English version is Elite Beat Agents. Through this one is more crazy and fun.

Greats:
- Tetris DS
- Advance Wars Duel Stike
- Resident Evil Deadly Silence
- Bleach 1 and 2nd (Inports)
- Theme Park
- Final Fantasy III
- Super Mario 64 DS
- Yoshi's Island DS
- Elite Beat Agents

Congrats and some good games are.

pokemon,diamond or pearl both great games

mariokart ds,An amazing game good graphics and very very good replay value

and much much more hopefully that will help.and i forgot to mension the new zelda phantom hourglass coming out soon.

pokemon zelda mario kart new super mario bros