I was wondering whether, as well as the simplicity and nostalgia associated with retro tunes, they are more popular for remixing because a lot more people will recognise them and will be able to tell when a remix is really good and has done something original. Newer games may be less popular not just because most of them are more complicated and may have vocals, but because they haven't had time to really circulate and grab peoples attentions yet.

Now I'm curious as to whether that happens with other types of music remixes as well. Hmm....