When I go on about the state of TV animation in the first half of the 80's, I should remember to stress that it was worse in the 70's, and that I'm basically talking about US shows. There WERE some really good, groundbreaking shows coming through in this period - and nearly all of them were from Europe or Asia. This was one of them.
I wish my memories were a bit clearer of 'Spartakus'. I suspect I missed a lot of episodes, as I was leaving for work around 4 PM most days back in 1988 when it screened here. Still, I must have gotten to see it somehow, because I have many clear memories of it, though I have no memory of 'Mysterious Cities of Gold'.
'Spartakus' was a very colourful, rich and imaginative epic. marred slightly by the rather incongruous pirates (yes people really did have mohawks back then. I remember being at a gig where MOST people had them). I thought Bic and Bac were cute, though they were cuter in the graphic novels, where they didn't sing. The drawing style was rather unique, too - at least for animation. It bore a vague similarity to the work of underground French cartoonist Jean Giraud (AKA 'Moebius'), and certainly shared the French underground sense of the fantastical. I feel like mentioning that, although there were plenty of 'lost civilization under the Earth' yarns over the years, this one's precepts remind me rather a lot of Richard Shaver's infamous 'Shaver Mystery' stories which had everyone exploring caves in the late 40's for lost civilizations.
'Spartakus' was also part of an important trend in animation that started coming through in the very late 70's and early 80's. Not withstanding the brief prime-time fling of The Flintstones and co in the very early 60's, TV cartoons had largely been extensions of the original 7 minute theatrical short. Most of Hanna Barbera's shows from the 60's and early 70's were still of this format - three or four short cartoons parcelled together as 'The (whatever) Show'. After that we began to get more of the 30 minute standalone episode show, but they were still discrete shows which could be played in any order, and frequently were. What changed around 1980 was shows started coming in from Japan and then France which actually continued their story arcs spread over several seasons. 'Spartakus' was one of these, and according to my memory it was one of the best. I just wish that memory were a little fresher so I could feel a bit more confident giving it this high a rating, but whatever the case, I certainly remember it outshining just about everything else around at the time. Even today I can't really think of anything else that really reminds me of it.