Nintendo’s ace-in-the-hole is retro family-friendly platformers that take you back to happy memories of NES consoles. There are already two great Mario games on the 3DS:
Super Mario 3D Land, which marries side-scrolling with full-world Super Mario Galaxy-style play, and the totally 2D (with 3D effects)
New Super Mario Bros. 2. Honorable mention goes to Donkey Kong Country Returns 3D, a well-done port of a retro-style Wii game that loses nearly nothing.