Super Mario 3D World is an amazing game. It doesn't bring the innovation Mario 64 or Mario Galaxy brought, but as what I would classify as a "refined" entry into the Mario series, it is arguably the best.
What I mean is that there are two types of Mario. There's the refined, and then there's the innovative.
The string of Super Mario Bros 1, 3, and Super Mario World were a string of refinements with some innovation (vertical screen scrolling). They took what came before and refined it into an even better experience. More powerups, more responsive controls, more game mechanics (flying then gliding anyone?). The trend continued with the New Super Mario Bros series.
Mario 64 and Mario Galaxy were innovative. Mario 64 crafted 3D movement and the camera for virtually every 3D game in existence today. Galaxy innovated on the platformer genre with spherical platforms and playing with gravity. There's only so much you can innovate though so these are a bit more rare, and their follow-ups are simply refinements upon them (64 to sunshine, galaxy to galaxy 2).
As a "refinement" entry Super Mario 3D world is the best Mario.







