I don't really agree with this approach, it is like forcing somebody to watch all great sci-fi movies before he can go watch Interstellar. I do think they should watch all those great movies in good time and because they are great, they will still be fun/good to watch today.
The same with games, i've seen it with my own kids. The real gems from the 8bit NES / C64 era still stand their own. I never forced them on these, but the questions come anyway, if you know kids, they are always full of questions.
After playing mario galaxy, the question came if there are other mario games, at that point it is easy to introduce them to the past. I showed/played them through the whole history of Mario, starting with donkey kong (and showing donkey kong jr on my original savoured game&watch), going to mario bros (no, not 'super mario bros'), etc. Did they like all of them, no and i don't blame them, because some of them are not that great anymore. But the real good ones were still enjoyed and played (by them, by choice afterwards).
Games are part of our culture now, like art, books, music and movies. It would be cruel not to let them know the classics, but it is just as cruel to force-feed them.