my favorite DS games are
New Super Mario Brothers
Metriod- WiFi is what makes this game even better.
Lost Magic- this is probably the best (and least known about) game I have, it has WiFi, and a relatively good storyline. THe WiFi can the a tad laggy, but it usually goes away as the match progresses.
FFIII- This game is amazing, im only about 7 hours in, but it is really good.
DKR- This was a un game, I got it for the Wifi, but getting TT was a little frusterating.
Adcance wars dual strike- this game was really really good. I did not finish it because I lost it, but I played 95% of the game, and it was really good.
DO NOT GET WORMS FOR THE DS!!! IT IS HORRIBLE!!