Well for me the best DS game is Mario kart DS it  had amazing gameplay with good graphics plus it was the first time the mario kart series went online,for me is the best Mario kart in the whole series.

Runner up:New Super Mario Bros.

Brain Age 1 + 2 >_>;

Megaman ZX

Runner ups:

Final Fantasy III
Megaman ZX Advent.

Elite Beat Agents.

ctk495, my decisions are the same as yours.
Including the runner-up.

 I don't have one, but the game that might make me buy one is FF4 remake, also FF3.

EDIT: Possibly DQ9 also. I guess I will be getting my hands on a DS then. 

what he said

2nd best is Pokemon Pearl

@BottledSpringWater
Wow awesome i knew somebody will agree with me.

Final Fantasy III
Pokemon Diamond and Pearl are the runner up.

I've been digging Entrian Odyssey, got a nice old school dungeon crawl theme to it, and it isn't bogged down in a lame attempt at telling a tripe filled story that no one in their right mind would ever get emotionally involved in (you hear that 98% of today's RPGs? I'm talking to you!)

But for lasting value, gotta go with Jump Super Stars, can't beat a Super Smash clone with Goku and Luffy beating the snot outta each other.