Zelda Wind Waker does have very beautiful art direction. Although, while I do like the cell shaded look, I can't say I'm 100% on board with the stubby character designs. Now, if I had to choose a game as having the best art style I'd go with Tron 2.0 on PC. I think it looks even more visually stunning that Tron Legacy. I also really like the Metroid Prime series visual style as well as the Portal games.
Then there's Panzer Dragoon Saga. It's not the most impressive game from the 32bit era, and let's face it, 3D games from that generation haven't aged well. But in my opinion it has some of the best art direction in all of gaming history. No other game looks like Panzer Dragoon Saga, other than the other Panzer Dragoon games. Sometimes the game looks so good it's hard to believe you're playing it on a Sega Saturn.
