Sunshine is an amazing game.
They took the basic controls of Mario 64, and looked at the 3D platforming in general and created a game that perfected Mario controls, and really fixed most of the problems with 3D platformers.
It made Wall jumps accessable and fun to accomplish. It incorporated tightrope antics, and a device for floating and shooting enemies in a fun whimsical way.
The two biggest problems with Sunshine was that it was Evolutionary game develop instead of revolutionary like Mario 64; and it took place all in one environmental location, and people are used to environmental variety in Mario...though truthfully, Sunshine's environment stability was a breath of fresh air to me.
The two biggest improvements with Sunshine was the "classic" puzzle like challenges in the game. Those challenges included some of the best Mario level designs ever. And the control. From being able to effortlessly, Backflip, slide down a wall, Spring off of the wall, activate your Fludd device and hover to a tight rope...Mario never controlled BETTER than he did in Super Mario Sunshine. And honestly very few platformers even today control as flawlessly as Sunshine does.