I will try to give my opinion about the french success of Goldrake here, even if I'm really not a specialist. I was 3 at the first broadcasting in France in 1978, but I can remember it was an immediate success. Why ?
Primo, I think that kind of anime was really new in my country. I have to precise that Goldrake was broadcasted "alone", without the other Mazinger or Getter Robo series before it (Mazinger Z only went for 12 episodes in 1987), so that was no example before of this kind of series of "big robots".
Secundo, Goldrake was really innovative, with a attractive chara and mecha design and a peculiar development which permitted to all the population classes and ages to empathize with the characters and find its interest in it. Even adults liked it (my mother said me once she was watching the series with me !).
Tertio, the impact of the series was so important in France that it still endures, and the children of yesterday become adults did continue to like it. From 1998-2000, I guess, there was a "revival" of the series here, with the beginning of the "DVD combat" you already know here (which came on "no DVDs because no rights in France"
). It coincided with the publication of the Gosaku Ota manga here. No series or nearly any had that effect, it became almost a myth for an entire generation, and even young people knows about it now, the transmission is continuing.
If you have questions, don't hesitate, I'll try to answer.
