My son was invited to a 9-year-old birthday party with this movie as the centerpiece, so I watched it in advance and had to say NO. Even with its charmingly antiquated animations, it's genuinely terrifying for a child. Not just swordplay and blood, but things like a mother and baby, both screaming, put into a coffin and thrown into the ocean. The Medusa scene is really suspenseful and gory, even if it's fake. And though my son sees the people in our family naked all the time, he's never seen nudity on screen and I think there's a difference, especially when you've gathered a room full of 9 year olds to watch it together. There are no children in this movie - and there's nothing in it to suggest it's a children's movie.
While this wasn't a great movie, it still is worth watching as a version of the "Perseus" myth, albeit heavily altered.
I saw this for the first time probably when I was 12 or so, and found it disturbing and shocking. There is a fair bit of bloody violence, and the scene with Medusa is extremely intense. Also, those who are used to the MPAA's current standards may be shocked by the three short (but not entirely necessary) scenes of nudity.
This would be a good alternative to the 2010 release. The nudity is very brief and not very sexual. Along with "Jason and the Argonauts," it is a good example of stop-motion photography techniques. It could be a way to introduce Greek myths as an interest for self-guided study and reading.