From the pics it looks like the wii is doing simple bilinear filtering. This often makes the image look too soft. More advanced filtering schemes like the Hires filter in Magic Engine or 2xsai typically give better results.
2xsai and the like are nasty. I can't see why people like those filters. They totally distort the image. What they need is a sharper bicubic filter and the options of 25/50/75% scanlines for 480p mode.