In short those two do not deserve to stand out as the two "Best Looking" Wii U games. I think Zelda U, Smash, 3D World, Yoshi's Wooly World, Splatoon, Pikmin 3, ect all LOOK exceptionally well on the Wii U.
Saying that, I will say Xenoblade Chronicles X is by far the most ambitious Nintendo project to date. it has the goal of being a vast, seemless open World shooting for 60fps. besides Zelda U, none of those other games can even begin to compete in the sheer computing work load it is going to put on the Wii U. With this and Zelda U we will basically see (granted there are always exceptions to the rule) exactly what the very limit of the Wii U is.
(I edited because I figure I should talk about Bayo 2 as well) As far as Bayo 2, I think there is a LOT of love from the developer to make the absolute best game they can for the next installment of Bayonetta. I think it has only helped them only being on one platform and they have optimized for it better than any other 3rd party game I have seen. Saying that it doesn't LOOK really any better than Pikmin, Wooly World, Smash, or 3D World. It has realistic textures, and that's about it. In fact, the last footage I seen the aliasing looks worse than all the others. Still it looks like a major painstaking labor of love project I can't wait to get my hands on. Bayo 1 looks the same. I would love to see some raw footage of it being played, and having all of the Bayoverse on a Nintendo console is awesome!
