This is something for which the effect you don't really see on Wii for some reason, and maybe I'm biased. I use a TV Box to convert all these video inputs into monitor friendly output, and boy was I shocked when I switched from a PS2 composite cable to a PS2 component cable. No, this is not 480p, no funny tricks of any sort. It is just the plain awesomeness from a simple cable change.
Just a simple cable change for an aging console which outputs in 480i produces a dramatic improvement in picture quality. So if you've got a brand spanking new TV with component inputs - don't skimp. Buy those new component cables for your PS2. It'll put your Wii's 480p output to shame. Maybe. (At least through a TV Box. :P)
Just goes to show new cables can indeed breathe life into old consoles.