Here are a couple animated films that have been mostly forgotten:
Marco Polo Jr. vs The Red Dragon - This film was actually Australia's first animated film ever. It was released in the states simple as "Marco Polo Jr." and tells the story of how one of Marco Polo's descendants has to return half of a medallion to its rightful air, the princess of Xanadu, before she is forced to marry an evil usurper. It's a fairly generic story, but it was also quite entertaining. Sadly, this animated film is better known these days as "Marco Polo Jr.: Return to Xanadu", which is an atrocious "remake" of the film (new animation is spliced in with old animation and the original voices are replaced with horrid voice acting).
Strit og Stumme - Known to English speakers as "Subway to Paradise" or "Dreaming of Paradise", this Dutch film is an interesting story of how an humanity, after living underground for so long after destroying the world, tried to return to the surface while escaping their overlords, a master race of bipedal rats.
Hugo a Vizilo - Yes, Hugo the Hippo, a Hungarian-American film that tells the sad yet noble story of baby hippopotamus Hugo. It will likely never be released in America today because of its psychedelic flair and some disturbingly violent content.
Asterix films - Sadly, "Asterix the Gaul" never caught on here in the States, even though he's a cultural icon in Europe. There were several French animated films made of some of his comic albums, such as Asterix and Caesar's Surprise and Asterix in Britain, all of which received English versions.