When plugging an old video game system with the usual red,white,and yellow cables into back of a hdtv, there’s no signal from the console to the tv. Why is that? Dreamcast and Xbox360 work fine but connecting Nintendo64 or Genesis/Megadrive it’s just black.
Any idea what could help? Any help is very appreciated.

I have a normal flat screen tv, i am planning to buy a new HDTV or lcd monitor ( depending on which is better) . The only reason i will be using my display unit will be for gaming ( using my xbox 360). Any suggestiions on which is best for gaming?