All tv's are HD capable, but not all tv's offer 480p and higher resolution. I feed a Toshiba Cinema series CRT an HD signal, and although the final picture is 480i, the result is incredible. S-Video has been around many years and very old technology by todays standards. Remember the Commodore 64 from the 80's? It came with S-Video cables. They can only carry a maximum of 576 interlaced lines of resolution.
Component is more recent, and divides the primary colors for an overall better picture. Component is capable of producing 480p, 576p, 720p, 1080i, and 1080p signals - even though it's analog like S-Video.