Some people like this game, some people hate it. I love it.
Story: Mario and Co. are on vacation to Isle Delfino. But Mario is told he needs to clean the entire island! Why? Because the perpetrator(later revealed to be Princess Peach) who looks like Mario is doing it and they think it's him. Once Bowser is defeated, they celebrate. Pretty good, I'd say.
Game-play: If you think this game is going to be easy, think again. Out of all he 3D platforming Mario games, this was the last one I beat. Why? Frustrating levels, tear-jerking bosses, and confusing physics. The final boss fight wasn't that hard. Just super ground pound the marked platforms. But getting there was another story. This really wasn't necessary.
Overall: Super Mario Sunshine is way too hard for some gamers, but I'd get past that and say 9.5. Great job, Nintendo!