Zelda OoT, Super Mario 3D Land, Mario Kart 7, Kid Icarus: Uprising, Kingdom Hearts 3D, Fire Emblem: Awakening, Pokemon X/Y, and then Zelda ALBW in November are the games I'd start with.
3DS has a very impressive library for only being 2 1/2 years old, so there's plenty of great games available (I have 21 retail 3DS games currently). The ones I listed are just some of my personal favorites and the ones that have seemed to get great reviews AND be praised heavily by fans.
Upcoming Games To Get
Definite: Kirby Star Allies (Switch), Mario Tennis Aces (Switch), Fire Emblem (Switch), Yoshi (Switch), Pokemon (Switch), Kingdom Hearts 3 (PS4), Monster Hunter World (PS4)
Considering: Fe (Switch), Donkey Kong Country Tropical Freeze (Switch), The World Ends With You (Switch), Ys VIII (Switch), Street Fighter V: Arcade Edition (PS4), Kingdom Hearts 2.8 Remix (PS4), The Last Guardian (PS4), Shadow of the Colossus HD (PS4), Anthem (PS4), Shenmue 3 (PS4), WiLD (PS4)
