Games like Super Mario 3d World or 8 player Smash (yes, 4 player Smash is online) could have definitely done better with an online experience considering they are multiplayer games.
Smash, I can agree with, because that's the core of the franchise. However, do tell me how Super Mario 3D World would be better with an online experience?
It's a multiplayer game
Ok, let me rephrase: why would Super Mario 3D World be better with an online experience?