i remember that legend of zelda: a link between worlds was lots of fun

Phoenix Wright series

Luigi's Mansion 2

Rhythm Paradise Megamix

Install TWiLight Menu to emulate a lot of consoles.

Fossil Fighters, two games on the DS and one on 3DS

Kirby Mass Attack

Captain Toad Treasure Tracker is fun actually

Mario & Luigi series, especially Bowser's Inside Story

There's also a GBA emulator for the 3DS if you want to broaden the range of games.

Picross (regular and 3D) are great on this, and Meteos still holds up as a unique puzzle game

You gotta play the Yokai Watch games. They're phenomenal! Definitely some of the best games on the console. They're also some of the biggest, it's impressive how much the developers managed to fit onto a 3ds cartridge.

btw you should know that the 2nd game did the Pokemon thing where 2 versions (Bony Spirits, Fleshy Souls) got released together with a 3rd definitive version sold later (Psychic Specters). The 3rd game did it too, but only the definitive version got localized so don't worry about it.

Fire Emblem Awakening and Echoes, Kirby Triple Deluxe and Planet Robobot, and Kid Icarus Uprising are all solid

I guess a few of the good music apps were either rare in physical or expensive on the higher end on the web store.

spoiler bc long