I play most of them still.
They're all hooked up to a tv or have batteries in them.
I have a very complex system of A\V switches, also my XBOx is modded and can play things like NEs, SNES, N64, SMS, Genesis, GG, GB\GBC\GBA and PS1, so I don't need to have EVRYTHING hooked up.
The main reason I have so many is cause I don't sell any when the next generation comes. That and I go to a lot of garage sales.