World Masterpiece Theater time again. And you know that means…
ORPHANS!
I hoping that is the 70's introduction rather than the 90's remake by the way. Correct me if I am wrong.
Right, this is another example of orphan-tainment hailing of course from the 19th century, when orphans out numbered people with parents 2 to 1. Based on the novel by Ouida (the pseudonym of the English writer Marie Louise de la Ramee), it tells the tragic tale of the orphan Nello and his dog Pastrasche.
The anime keeps the ending of novel and I'm guessing the impact of that is part of the reason of it's position in the chart. As well of course, the exemplery animation work of Nippon Animation. Check out the comments by zak2000 and yoimati on that page btw, for an interesting insight into how kids shows were treated in Europe.