I'm using a 60ish inch 1080P LCD Samsung Smart 3D TV and am sitting at least five to six feet away and the game looks great. Of course, if I stand a few inches away the pixels appear. Maybe the Wii U default settings aren't working well with your TV, you're sitting too close, or your TV has a bad upscaler.
And I can't stand playing off screen TV unless I have to because the colors look less crisp and vibrant compared to the TV. The little texture details are gone too like the ones on the asphalt road in MK8.
Hope you fix your problem!











