This seems familiar. Did you post the same uestion at digitpress.com?
The answer is: No. And yes. The reason for the contradictory answer is because the quality depends upon the game. If the game is capable of doing 480progressive, or 720p, then you'll see an improvement.
If the game can not do progressive, you'll see no improvement over S-video cable.
I did post it somewhere else but that site doesn't sound familiar. Okay, I will prob end up doing component cables just to have the best for whatever games I play.
They make some games look much better for me. I got a new 42" HDTV a couple weeks ago and component cables for my ps2, and the games that are capable of progressive scan look much better, especially Socom.