Art style trumps sheer graphical power any day of the week. It's because of that that Super Mario World and Windwaker are going to stay near the top of my "looks good" list regardless of how many generations go by.
From a power perspective though, X and Bayo are the most impressive so far. The scope of Nintendo games have never been like X and Bayonetta, they'll both be the first of their kind on the Wii U, and the art styles are drastically different than something like Mario Kart 8, which itself looks amazing. I don't think they'll be more impressive than the future installments of Zelda however.
Graphics are the absolute lowest rung on the ladder for me though. Anything at MGS3 on PS2 level of graphics or above and I really stop caring. Like the thread with the PS3 vs PS4 versions of Watch Dogs. Those screen shots might as well be the same to me for as much as I care, as long as you can get the frame rate to be consistent. It doesn't mean I don't appreciate graphics when they're good, I just mean that after a certain threshold they mean absolutely nothing to me in my decision to purchase/play a game.