This morning I played a Super Famicom using Gamestop's universal S-Video cable and the picture looked great.
There is a faint kinda grid pattern across the screen, kinda like the effects I see with my modded SMS and Genesis systems, the XMD-2 and similar to the Genesis 2 and CDX picture with a regular AV cable(only barely noticible). Its kinda like your SAI photo, but the dark spots are light spots instead and not so annoying. It didn't look like half the color was missing or anything.
The image remained solid and consistant the whole time. Since the clarity was a huge improvement over composite, I have no problem playing games like this. I couldn't find any of my dedicated Gamecube S-Video cables to test.
This cable was something like $7 at EB if you'd like to try it out.