Alright.... So we are going to ignore ALBW, which many people claim is the best Zelda game since Wind Waker...... I get it if you aren't keen on SS(I personally thought it was amazing), but ALBW is pretty objectively good.
Enough said. Also, with the new Bow mechanics alone, and comprehensive horse AI, Zelda Wii U looks to be more than slightly innovative. We haven't even truly seen the game yet as well!
That is some broad statements and comparisons for a game that is already released, and a game that we have on seen 4 minutes and 42 seconds. Furthermore, Nintendo really doesn't want to classify Zelda Wii U as open world. They are merely taking the original LoZ, and expanding it to a gigantic 3D plane.
Everything we have seen so far as well, has made Zelda Wii U look that way. This is the Zelda series after all, and they are known for it's secrets.
This is a downright lie. Xenoblade X is at least twice as big as The Witcher 3.
Witcher 3 clocks in on a world of about 139 square kilometers. Xenoblade X clocks in at about 200 square kilometers, at the very least. But I would like to mention that size does not always equal greatness. I would very much prefer true Zelda Dungeons, secret quests, and that Zelda charm to just a big world. I am not saying that Witcher 3's world isn't impressive, but Zelda Wii U has the creative prowess in EAD3 to outmatch that.
Regarding on blandness, they seem pretty on par with each other. I want to explore every inch of both worlds. Though I have to say, Zelda Wii U is going to have a more timeless artstyle regardless. Not only that, but Aonuma confirms that the game looks even better than this. Though Zelda Wii U seems to have a better draw distance than Witcher 3 as well.
I think you are also comparing 2 totally different things as well. The Witcher, is more or less, an Open World Western RPG. Zelda Wii U, is an open World adventure game. Zelda is going to have the strengths of puzzles, exploration, secrets, and collecting. Witcher 3 has more of an emphasis on Combat, Lore, and player choice. They will both be as equally good, and I highly doubt the Witcher 3 could outshine Zelda in that way.
Overall however, you definitely can't say it either way as we barely know anything about Zelda Wii U. We need to wait until we get substantial information instead of yelling insults at a game before you even know what its called.