Edit – The behavior above is to be expected if you feed in PAL consoles.
I’ll drop Mike an email and ask him to look in on this thread too.
We know from experience that Genesis/Megadrive does tend to have widely variable quality composite, so that could explain that.
do you have any better quality connections to try? For PS2 for instance, it should be cheap and easy to move up to component which would give you a huge boost in picture quality.
I’ve not tried SNES or NES with mine as of yet, my NES doesn’t output composite any more sadly.