I recently cracked my 3ds (which is super easy to do now that they've stopped updating it) and you can use it to play any previous generation games (up to PS1). Wish I knew that before I bought a purpose-made console lol
I have a huge catalog of games but since I'm switching out my SD card for a bigger one, I'm looking to basically just download whatever seems interesting. What's your favorite 3ds and nds games? (Please don't say Pokémon)
For DS Games Rhythm Heaven is really fun, it's basically a collection of rhythm mini-games. Another good one is Mystery Dungeon: Shiren the Wanderer, from the same series as Pokemon Mystery Dungeon but with less focus on the story and more traditional roguelike mechanics. For 3DS, someone already said it but Shin Megami Tensei IV is a fantastic RPG.