[my3rdskyline]

component video is better than S-Video. here's how it works sort of
composite: one yellow cable. all colors, refresh, and sync in one cable. very compressed and not good quality.
S-Video. the colors are all in one cable, brightness are in another and the refresh and sync are in other cables. good quality.
component: separate cable for each color with the sync compressed. Better quality than S-Video. If your TV has component video, USE IT. it's the best (unless you've got a DVI input)
DVI is a direct digital connection. Not sure if the cable layouts are exacly right because that was off the top of my head, but I'm sure the quality is this order-> composite, S-Video, component, DVI.
Hope it helps