Some gems off the top of my head:

Action / adventure
Assassin's Creed II: Discovery

Fighting
Marvel Super Hero Squad (I'm serious, it has a very nice SSB-esque fighting engine)

Puzzle
Picross 3D

Racing
Speed Racer (it's a film tie-in, but it's really good)

RPG
Cross Treasures
Lufia
Pokémon (duh)
Soma Bringer

i can only think of one other good racing game

Racing
Sideswiped

Some great games that weren't already listed:

Action / Adventure
Castlevania Dawn of Sorrow (OOE is better, but this one is also great)

RPG
Shin Megami Tensei: Strange Journey (don't trust gamespot, they don't know a thing)

Graphic Adventure/Visual Novel/etc.
Another Code: Two Memories
Hotel Dusk: Room 215
Phoenix Wright Saga

Strategy / SRPG:
Both Advance Wars
Disgaea

Other
Elite Beat Agents
Trauma Center
GTA: Chinatown Wars

I just remembered the great Soma Bringer OST while reading the previous list, it was really good.

RPG:
Dragon Quest: Zenithian Saga (IV-VI)
Dragon Quest IX: Sentinels of the Starry Skies
Dragon Quest Heroes Slime
Fossil Fighters (one of the sweetest games on the system)
SaGa 2: Hihou Densetsu - GODDESS OF DESTINY (full translation available)
Tales of Innocence (full translation available)
Solatorobo: Red the Hunter (EUR version will be released the 1st of July)
Mario & Luigi RPG 3: Bowser's Inside Story
Inazuma Eleven

VN:
Last Window: The Secret of Cape West
999
Apollo Justice: Ace Attorney

Fighting:
Jump Stars series (both are translated)

Action
Bangai-o spirits.

Great action shooter and level editor!

This post has been edited by noahkorevaar, Wed, June 15th, 2011 at 09:53

Dragon quest heroes: rocket slime

A very nice Adventure with a lot of collecting, nice humor and "GIANT TANK BATTLES":

I didn't really think Strange Journey was all great. I quit about three times, in about the same place.

Trying it again, however. I will simply cheat my way through the game if I have to.

More on topic;

N+ is neat platform(?) game.

This topic pops up every now and then.

http://www.ds-scene.net/?s=viewtopic&id=2236
http://www.ds-scene.net/?s=viewtopic&id=2901
http://www.ds-scene.net/?s=viewtopic&id=3436

There're probably more topics 'bout it out there, but I was just looking for the latter one (and came across the other two while looking)

And every time it pops up again it's worth it.

[EDIT]


I don't recommend you playing it if it feels like a chore. The story is alright but it isn't something so great as to play the game till the end, cheating your way for the sake of it. I love the gameplay, I enjoy exploring every map square in each dungeon looking for hidden doors and demons, fusing them, experimenting, finding some demons that seem unbeatable and tuning my party to match their weaknesses, etc... I don't think you'll like it at all if you don't enjoy the way it plays.



This post has been edited by sarkwalvein, Thu, June 16th, 2011 at 00:12