My condolences for trying to play Hyrule warriors on a non-new3DS model. I commend your bravery.
Seariously though, expect some major slowdown. Still playable I think(?), but do not go in expecting anything amazing. It's already pushing the new3DS to its limits.
That said, as someone who just adores the Mana artstyle, keep an eye out for Ever Oasis. If you get it for a cheap price it should be a good romp. Gets a bit long in the tooth in late game since the core gameplay loop is a bit limited, but it's cute as fuck and a great pick up and play for ten minutes game.
Even without the Miiverse support for easier sharing, Mario Maker might be your thing. It's fun building your own level and explore the creations of others.
Monster Hunter 4U. Obviously depends on your willingness to brave the gameplay mechanics, but if you get hooked, you will spend hundreds of hours in this game
Steamworld games. Dig and that other one. On the eshop.
Same as Fullblox, Gunman Clive, Shovel knight (if you haven't played it somewhere else yet), olliolli, and the Boxboy series.
Animal crossing (any version, the old non-Amiibo version has a free patch on the eshop that makes it the same as the repackaged Amiibo version). Of course, once again it depends on your gaming tastes.
Fantasy Life is a cute hack and slash and bow and arrow and fireball and etc game with moderate multiplayer support. Plenty of fun, even though it can get a little grindy if you're a completionist.
Smashbros and/or SF4 if fightan gaems are your thing.
Rune Factory 4 for the uguu harvest moon experience.
Plus a whole shitload of other games I can't remember now.
