I believe Keranu had a problem capping composite from one of his systems,but the others were fine on his cap card.
Not only that,your comparing composite out from the Wii,a system that produces a higher res and was built in 2006,with higher grade components for composite output,running a game in emulation on a 256 bit graphics chip.
That and this is like saying every composite signal should be at the same strength and interpreted the exact same on any and every product,and in a perfect world it would be,but its not a perfect world,and every tv model uses different chips for its comb filters for composite input,and cap cards are very much like this also,some of them having very weak comb filters because they are mainly designed to cap s-video quality and are designed to be compatible with composite. You can take a composite signal and use it on 2 different tvs,one that is built to do very good composite,and one thats just made to be compatible with it. Ones built to be compatible tend to do really well with newer electronics like Dreamcast,PS 2 and Gamecube on up,and dvd players,and tend to look average with older electronics like VCRs,composite laserdisc players and older game systems.
These days it is getting harder to find a tv that produces good picture quality off of a composite signal of a older system. So you saying composite looks like ass on all your tvs just tells me your tvs suck at composite,and are prob best left doing s-video work. It seems like your trying to turn this into a debate like your experience dictates everyone else's with composite,which it doesn't,and every ones set up is different and their milage will vary picture wise. What would be cool is for everyone to post pics of their system running a game to show their pic quality. I know this is kinda hard compared to using a cap card,but were not supposed to be talking about cap cards here,not everyone plays their game systems on cap cards,as most use Tvs.