Since you already own MK7 and Revelations, i can recommend to you Super Mario 3D Land, Ocarina of Time 3D and Kid Icarus: Uprising. Those five titles are my personal must-have list on the 3DS right know.
Then you might want to check some tier 2 games: Dead or Alive: Dimensions (really great fighter, almost as good as SSFIV and it feels like a complementary experience to the capcom game), Starfox 64 3D, Tales of the Abyss and Metal Gear Solid: Snake Eater 3D (bear in mind that those three are ports)
there are some nice things on the eShop too. Pullblox (Pushmo in the USA) is a must buy puzzle game, and Mighty Switch Force is a great game, even if a tad short. Most 3D classic games aren't worth the money, but you should at least check out Kirby and Kid Icarus.
Last but not least there are lots of classic gameboy games to try. you should at least get all the Mario Land games, Zelda: Link's Awakening, and Donkey Kong (this one is really great!)
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