I've bought a Panasonic Viera recently and it can upscale any source to 1080p. My Wii games have never looked so clear and crisp. In fact even better than some of my xbox360 games and it makes you wonder if they can make it even better. But ofcourse my common sense is telling me COD4 graphics aren't possible on the Wii, and it's just the amazing visual artstyle that games like SMG and MP3 are using that is so amazingly good to look at even on lower resolutions.
However I have read a rumour that the Wii's GPU is capable of running HD games. Perhaps that they will fix this with a firmware update some time in the future. That's about as close as it can get to COD4 graphics and it's still way off.
http://www.nintendolife.com/articles/2007/02/17/rumour_wii_is_hd_afterall
