Softmod it and just dump every rom off of anything. I mostly play og DS, GBA, and SNES games on mine at this point.

Check out Electroplankton, Rhythm Heaven, Elite Beat Agents, Phoenix Wright, Professor Layton, and Trauma Center games. I think they’re my faves that use the DS/3DS format.

Shin Megami Tensei IV (and IV Apocalypse after that), Devil Survivor 1 & 2, Persona Q, Fire Emblem games are all a good start if you like JRPGs

Pokémon OMega ruby alpha sapphire or Pokémon heart gold/soul silver. Best Pokémon games.

Somehow Kid Icarus Uprising hasn’t been mentioned yet, definitely a top 5 game on the system. Also grab Elite Beat Agents, my favorite rhythm game of all time and the inspiration of later rhythm game Osu.