S-video isn't overrated at all if you have a good TV that supports it. The leap from composite to s-video on any system I've used it with have been well worth the cost of the cables. Even made the text that was unreadable over composite in a few PS3 games readable before I got my HDTV.
And I'm sure RGB is better than s-video, but sets supporting RGB just haven't been common in the US, so for most of us that's why s-video was the way to go before systems started using component and HDMI.