Maybe not the ultimate answer but it needs to be honourably mentioned: Isle Defino.
Excellent music, a lively hub with minigames, secrets, shines, characters, events that afterwards lead to beautiful portals to other zones that you can slip and slide on your belly to and then jump up and turn into paint as you get sucked into that stage. There was also a gimmick where things got brighter the more shines you found so that Mario had to wear sunglasses eventually.