ok i have 4 different ones so should be able to help here
Official nintendo component cable
XCM Multi-Console Component cable Version 3
Game branded component cable
Unbranded wii component cable (came free with something i bought)
every cable gives the same picture quality, the 3rd party/unbranded cables show no quality difference between the official cable.
I have had 3 hdtv's since having my wii on launch and its been the same results on all of them so it isnt actually dependant on your tv either, official or 3rd party cables, they are all the same