They're definitely in the top echelon, but I'm undecided on whether they are the top two.
Other games in the category include Endless Ocean (1 and 2), Super Mario Galaxy, Super Mario 3D World, Mario Kart 8, Super Mario World, Donkey Kong Country (1, 2, and 3), the Ace Attorney games (prior to Dual Destinies - lower due to 3D characters not being quite as good at this point), Yoshi's Woolly World, and Harvest Moon: Friends of Mineral Town.
It's not all about technical quality, which is why there are SNES, GBA, and DS games on the list. If we're talking not just "best looking" but also "most impressive", then yes, Xenoblade X and Bayonetta 2, along with Endless Ocean, are top of the list, in my view.