Also, the image quality is terrible on most of those "plug em into the TV games". The only one I have ever seen that puts out a quality picture is the Genesis one.
The worst one is the Space Invaders one. Not because of image quality, but because it doesn't have the real space invaders, it has a copy of that terrible, terrible bootleg Nes version of Space Invaders that has huge spaces inbetween each invader and the next one. I couldn't even spot what version it was at first, I just said "what is this crap?". I later found that same version on a bootleg Nes clone unit as well. Oddly enough the Space Invaders one has a darn near perfect port of some other rare Invaders era games and then a bad version of Phoenix.