The colors, the colors. Miyazaki absolutely perfected the use of colors, I think he spent a lot of time choosing the right shades and brightness to each one in every scene. And in all his movies that has a main theme of childhood these colors are absolutely stunning, in Ponyo it is even more crisp and clear. It's the same colors that adults remember only from when they were children, the perception of reality is super colorful and he makes it just spot on.