RF ---> Composite ---> S-Video ---> RGB/SCART ---> Component ---> HDMI

Sega Genesis does not have Component, though I suppose it could be modded.

Component started with Progressive scan TV's which were the bridge to HDTV. I do not think than designate HDTV, they simply have the capacity to carry an HD signal where as S-Video probably does not. Component is roughly similar to RGB/SCART though it came after.

Much does depend on the TV you are displaying your material on. A Sgea Genesis outputting RGB is superior to RF/Composite/S-Video with the correct monitor, but might e indistinguishable on your everyday CRT/HDTV.

Some of the guys here know better than I and will hopefully chime in.