One thing that just occurred to me.... The sound on the 2600 sucked less back then the harsh sound we hear now is from infinitely better speakers we have now, back when the 2600 was new speakers produced a almost muffled sound, like CRTs made old graphics look slightly better.
I think a few of the early systems could benefit from that, at least up to the 8 bit generation, by the 16 bit generation I think TVs had gotten a lot better in almost every way