Weak.

Playing Wii over component cables the games always looked good to me. Now in Wii Mode over HDMI it looks about the same. The difference, provided you were using component, really depends on how your TV interpreted analog signals. HDMI is always pixel perfect, kinda boring that way actually.

Bottom line, when playing the original Wii, use these babies:

Honestly didn't notice the difference. However, based on what people are saying, that's probably because I used the good old component cables with the Wii. Now those things made a real nice difference. Galaxy 2 with component cables was honestly one of the most gorgeous games of the last generation on any console. (obviously not from a technical standpoint but from just a pleasing to the eye standpoint)

twilight princess looked terrible on my 50 inch tv. honestly it makes.no differance playing on wii u unless its on gamepad then its gonna look better cos on smaller screen

I'm pretty sure that Wii games on the Gamepad look quite a bit better, but I doubt they look much better on an actual TV.

It upscales the resolution, but texture quality and jaggies stay

A 1080p TV with HDMI ports but without a scaler? Do these combinations exist?

What TV-model do you have?

In SkyWard Sword for example, the color of the Sky in Wii in more Cyan, in the Wii U more bluish... And in others games I can see these differences in the colors... More probably related to the output of each console, than any programming.

P.S:

Guys for those who still own old consoles and enjoy playing them, I have a Samsung PL43E400U1GXZD  EDTV, It's 43in Plasma TV. The Wii games are crystal clear in it, because its panel is 480p Max.

That;s the difference between playing Wii games with composite (480i) vs component / HDMI (480p) which is what the Wii U defaults to. Games like Prime 3 and Galaxy 1 & 2 looked amazing when I had my Wii hooked up to my 50" plasma via component cables.