3D World is the best pure 3D Mario game. The courses are generally great and varied and the several different playable characters, including Princess Peach, make for several approaches or playstyles being possible. Oddysey is... nice. But it's more a Banjo-Kazooie/3D Sonic game with a Mario coat of paint. No powerups, no courses. It just doesn't feel like a Mario game to me.
So yeah, I want a 3D World 2. With Mario, Luigi, Peach, Daisy, Rosalina, and Toad as the playable characters in up to four player multiplayer. Because co-op 3D Mario is hilarious.