Super Mario Galaxy 2 was the best 3D Mario and took what they started with Mario 64 and perfected it, but the 2D games will always be the core of the series. Mario World was great and the Yoshi sequel may even be better, but none of the 2D games since Super Mario Bros. 3 have really come close to the evolution that game provided to the 2D platforming genre. It pretty much provided the formula that is still used today.