My controversial opinion, it's one of my favorite Mario games. Love the world and how it fits together, the vibrant colors and tropical setting, the ridiculously dumb story, and the water spraying and cleaning I actually find satisfying. Also loved the music and the side missions more than the side missions in either Mario 64 or Galaxy.
For the 3D Marios, I like Sunshine more than 64, but I like the Galaxy games a bit more than Sunshine, BUT IROnICALLY, some of my favorite Galaxy stages are Sunshine inspired.