Tell me how does something look 4x better? How do you determine that? I'm just going to say that super mario galaxy is significantly superior to all of those games mentioned in terms of technical acheivements. You see alot more shaders(Furs,Water Effects,etc) many more polygons, crisper textures, and superior lighting. All this and the game runs at 60fps with no framerate drops. So yep that is about the only Wii game that really seems to set itself significantly apart from those you mentioned. There are others that set themselves apart to too, but that is the only one that does it in just about every area. So I agree, and want to see developers put effort and make all of their games at least close to super mario galaxy in this area. I am fine though with last generation visuals, and I don't even see the HD upgrades as "next generation", in comparison of what the Snes was to the Nes, or the N64/PS to the snes, or even the XB/GC/PS2 to the PS/N64. Yeah I think it has come to the point where better graphics aren't too noticable, despite the technicalities. Though superior technology does allow for some art directions to be acheived easier. So to answer your question, there has been one Wii game to show a significant advance that you want, but I don't see too many from third parties in the future. I do see something from Factor 5, Retro, or any of the other developers that pushed the GC to also push the Wii, since they are very familiar with the hardware, and more specifically the TeV.

@OP The Snes, but I expect my answer to change to DS, by the end of its life.

the gamecube's problem is that rebel strike is probably the pinacle of visuals,  seriously it generally runs at 60fps