Keep in mind that RE: R is an exception, there's not a single 3DS game that looks even anywhere near that good.

Barely any textures in this game, just flat ugly colours.

even New 3DS couldn´t handle Super Mario Galaxy. So Wii was much more Powerfull, but because of the tinier screen, 3ds games look better.

The Wii obviously.

1. Why does that even matter? SMG is an exception to the Wii's library, yet people mention it. 

2. Dark Moon > Luigi's Mansion in terms of lighting and shaders. 

3. Luigi's Mansion > Dark Moon in terms of polygons and texture work.

3. The shading in Dark Moon is superior to much of what is found on the Wii. Only SMG really surpasses it. 

Dark Moon

Luigi's Mansion was a launch game for the GC.

SMG is not an exception. Look at DKC: R (the 3DS port is inferior in every way) or MP3.

Luigi's Mansion 2 is just ugly, like most games on the 3DS.

I know, but the Wii and GC have similar feature-sets and GPU capabilities, so the 3DS advantages (shading and lighting) should persist with Wii. Considering one of the most impressive GC games which competes with a lot of Wii games was a launch title (Rogue Squadron II) I don't see that mattering much. 

DKC:R is a 2.5D platformer, and it fits perfectly within the expectations of the Wii's hardware. The 3DS version isn't inferior in every way (I have both versions.) In most areas it remained the same, which is quite impressive considering the game was developed with the Wii's architecture, strengths and weaknesses, etc in mind. 

As for MP3, I wouldn't rate it anywhere near as impressive (technically) as SMG (albeit when one plays it at 1080p a lot of detail is revealed.) If we are going to include MP3, then we can include games like Ironfall, RE: Mercenaries 3D, MGS3D (which is superior to the PS2 version in many ways), 

MP 3 is probably more impressive as SMG. Check out planet Phaaze or Valhalla.

PS2 was even wea;ker than the GC.

I just replayed MP1 and 2 on big screen tv and it still looks miles better than any 3DS game I own. With bigger worlds to boot. Sanctuary Fortress can easily rival the best Wii games out there. I'll go even further: it looks a lot better than anything on Wii or 3DS.

And DKC: R 3D really is the worst version. Just look at the framerate alone.

I've played the game a dozen times: it is not. SMG has better textures, more varied and advanced shading techniques, higher polygon character models. MP3 benefits from larger environments, but that means very little when each door is a loading screen. 

Yes, but the 3DS version of one of PS2's best looking games is superior to the PS2 version by adding better lighting and shading techniques, which is the 3DS's strength. If we are to compare pure specifications, then this argument would be easier. 3DS (even before new 3DS) has more ram, a more modern GPU which supports programmable shaders, and a comparable CPU to the Wii.  

That isn't what you said. This is what you said, "the 3DS port is inferior in every way" which isn't true. In most ways they are the same. But this isn't a good example anyway. The game was developed with the Wii's strengths in mind, for the Wii's architectures. Of course it won't run perfectly on a platform that is comparable in raw power, but with different strenghts/weaknesses. 

The Wii by far IMO, but I still think 3DS has some great visuals.

SMG isn't even playable for me anymore, it looks that ugly on a hd tv. MP3 has much more detail.

This is Samus' face at 75% corruption, something most people didn't even see yet retro put that much detail into it. This amount of detail is found throughout the game. Don't tell me SMG pushes the wii more with its mostly very simple textures.