Absolutely fantastic list! Will definitely be cross-referencing this whenever I grab a surprisingly-easy-to-mod 3DS! :D

A couple recommendations of my own for this list:
Apollo Justice: Ace Attorney
Hotel Dusk: Room 215 + Last Window: The Secret of Cape West
Henry Hatsworth in the Puzzling Adventure
Sonic Rush + Sonic Rush Adventure
Fire Emblem Shadow Dragon
Grand Theft Auto: Chinatown Wars
Inazuma Eleven
Mega Man ZX + Mega Man ZX Advent
* Trauma Center: Under the Knife 1 + 2

@Fizza thanks for the suggestions! Not sure how some of those higher-profile ones escaped me, will be sure to include them. I always hear good things about the Inazuma Eleven games but I never bothered with them since I don't care for sports anime. I'm assuming this one doesn't require any knowledge or investment of the show? And actually, I kept the Trauma Centers off the list on purpose, games like that really gross me out, lol. No plan on playing those – but I'm glad you mentioned them so anyone wondering where they are has an answer now!

Came in here to suggest DIY just for the creative fun juices, and it's already here. Goooood. Probably my most cherished save file that I never want to be lost.

Solatorobo
Custom Robo Arena
Sonic & Sega All-Stars Racing (Actually a fairly good port that I played a lot back in the day)

Only things I can think of atm I'm afraid.

Here's what I've got for potential suggestions:

Chibi-Robo Clean-Sweep: Japanese exclusive DS sequel to the original Chibi Robo, got an English translation recently.

Guru-Guru: A somewhat obscure sports game compared to golf where you train familiars by throwing/hurling them across obstacle courses.

Trace Memory: Cing's first venture on the DS (you might know them better for Hotel Dusk), apparently utilizes every function of the system. Really looking forward to tackling this one myself.

Solatorobo: Steampunk action-adventure game that has some real twists and turns. That's all I can say about this one.

Retro Game Challenge: Parodies famous arcade classics of the 1980s with the gaming magazine cheats culture right around it.

Fossil Fighters: A monster collecting game often compared to Pokemon that is exactly what it sounds like on the package. You might also want to check out the sequel.

Tornado: From what I can tell this is basically a DS Katamari Damacy knockoff? I need to try this one out myself as well.

I could probably dig a bit deeper later, especially considering I'm planning on trial testing quite a few more DS titles in the future. There's other stuff not on your list that I know of, but I wouldn't necessarily include (i.e. 2.5 or below in my book). Hope this all helps!

Please don't play Lunar Dragon Song. It's truly awful in every way.

@FallenGrace oh trust me I've heard! Its failure is exactly what compels me to play it. As a newly-inducted fan of the Lunar series, it's my own personal self-imposed responsibility to see just how hard it falls.

Ha! As long as you know going in lol. It's still the only Lunar game I've played though I have the others now at least!

I'm going to use this list to look at DS games I need to play myself, thanks!

You missed Drawn to Life's sequel, Drawn to Life: The Next Chapter. It's SO much of an improvement in almost every way. Just make sure you get the original version and not the reprint, since the ending was changed in reprint copies.

the only things i could think of you've already got, was gonna say cookies and cream since that seems like a "you" kind of game in my head.

this is another reminder i gotta get around to AA investigations as someone who holds the og ace attorney trilogy as some of my fav games of all time lol.

also lunar dragon song was a game i got on ds as a kid and hadd no idea how to progress whatsoever in and forgot the name of so seeing this list teleported me back to aimlessly wandering around the starting areas of that game LOL.