My favorite would probably be Skyward Sword's art style. I think it's really beautiful. The impressionistic watercolor style is really great. I like it alot. Another one I like alot is the art style used in Ocarina of Time 3D. It really brought the world to life, and everything, even the sky, was wonderful to just look at. I also really like the cel-shaded art style in The Wind Waker. It really added depth to the world, and the beautiful colors helped me immerse myself in the game. Those would be my favorite art styles.