Here is the list in order of mentions, and then alphabetical order:

Chrono Trigger
9 Hours 9 Persons 9 Door
Ace Attorney: Phoenix Wright
Ghost Trick
Hotel Dusk
Might and Magic Clash of Heroes
The Last Window
Chibi-robo (Park Patrol)
Metroid Prime Pinball
Professeur Layton
Solatorobo: Red the Hunter
Soul Bubbles
The world ends with you
Aliens Infestation
Big Bang Mini
Bomberman 2
Broken Sword
Castlevania Dawn of Sorrow
Castlevania Order of Ecclesia
Castlevania Portrait of Ruin
Custom Robo Arena
Diddy Kong Racing
Disgaea
Dragon Quest Heroes: Rocket Slime
drawn to life
Elite Beat Agents
Fantasy Life
Final Fantasy Fables: Chocobo Tales
Final Fantasy Tactics A2
Fire Emblem Fates
Flower, Sun, and Rain
Golden Sun: Dark Dawn
Ketsui Death Label
Kingdom Hearts 358/2 Days
Kingdom Hearts Re:Coded
Knights in Nightame
Konami Classics Series Arcade Hits
Korg DS-10 synth
Lock's Quest
Lost Magic
Mario Basketball DS
Mega Man Zero Collection
Metal Slug 7
Meteos
Nervous Brickdown
Orcs and Elves
Osu Tatakae Ouendan
Pac Pix
Picross 3D
Point Blank (badly damages the screen)
Polarium
Professor Layton and the Last Specter
Resident Evil Deadly Silence
Rhythm Paradise/Heaven
Rooms: The Main Building
Scribblenauts
Shin Megami Tensei Strange Journey
Sonic Rush
Suikoden Tierkreis
The Brain Age
The Dark Spire
The Etrian Odyssey games
The Touchmaster minigame collection
Touch Detective 2 (and the 1)
Trauma Center: Under the Knife
Yokai watch

@mxfraud i really enjoyed drawn to life, where you have to draw the stuff you’ll use in the game, such has cloud platform and others.

From what i can recall (only played it once when i was younger) it was really refreshing and a smart way to use the tocuh screen

@mxfraud hmmm, i liked Final Fantasy Fables: Chocobo Tales if you're into final fantasy and ok with something cute and more aimed at children

Soul Bubbles is also a great original game that is not that well known

@mxfraud I have no idea if they're hidden gems or well-known gems :

• 9 Hours 9 Persons 9 Door is a point & click in a survival setting with interesting plot twists
• The world ends with you is an action RPG with moody teens and catchy songs

Thanks to you, i realised i have like... 15 DS games, and a big part of them are Professeur Layton 😅

@mxfraud Elite Beat Agents 😎

Edit : just saw Ouendan already recommended, EBA is part of the same series, but with musics well-known worldwide

@mxfraud Why specifically "Lite" ? I don't think there is any difference with the Tank or the XL versions.

My personnal list would be, in decreasing preference order:
_ Ketsui Death Label;
_ Ghost Trick;
_ Castlevania Dawn of Sorrow;
_ Castlevania Order of Ecclesia;
_ Metal Slug 7;
_ Touch Detective 2 (and the 1);
_ Konami Classics Series Arcade Hits;
_ Resident Evil Deadly Silence;
_ Last Window (in the same way you should play Hotel Dusk before, even it 's not as good);
_ Point Blank (but there is a downside : it badly damages the screen);
_ Might and Magic Clash of Heroes;
_ Aliens Infestation;
_ Shin Megami Tensei Strange Journey (I only played the 3DS version but it seems to be pretty much the same game);
_ Broken Sword;
_ Knights in Nightame (it's VERY difficult);
_ Bomberman 2;
_ Meteos;
_ Metroid Prime Pinball;
_ Orcs and Elves;
_ Flower, Sun, and Rain.

I'm not as fond of Chrono Trigger and Disgaea, but to be honest they are pretty decent games.

Castlevania Portrait of Ruin, Kingdom Hearts 358/2 Days,
Kingdom Hearts Re:Coded, Mega Man Zero Collection and The World Ends with You are ok or mildly good games, mostly with big issues.

Final Fantasy Tactics A2 was nearly an excellent game, but its gamedesigners made REALLY poor gameplay choices which destroy all its merit.

Also, the DS is compatible wjth GBA games, maybe you're also interested in a list of those ?

@mxfraud 🤔 I think most of the better stuff has already been mentioned, but how about

Elite Beat Agents or Polarium?

@mxfraud I know it's a big name but I don't think the series has truly been considered top-tier since its 90s heyday, so if you haven't checked out the Sonic Rush games or the DS version of Colors, they're worth a look. The Brain Age games' purported health benefits are dubious, but they're fun.

More actually obscure: The Touchmaster minigame collection is more fun than it has any right to be. (Alas, owned by AT&T, but you'd be getting it secondhand these days anyway so I'll give it a pass.)