Both of these movies are CGI - both very well done for the years that they came out in. Appleseed Alpha is a reboot of the Appleseed franchise with a new setting/storyline, similar to a Hollywood blockbuster in the same way that The Spirits Within is more of an action/survival story than a traditional anime. If you enjoyed one, you will enjoy the other. Both are stand alone movies (you do not need to know about the final fantasy games or have seen the other Appleseed movies in order to enjoy them), and the English voice acting in both is extremely well done and comprised of some of the best VA talents you could hope for. read more
Appleseed and The Spirits Within are sci-fi movies done exclusively with computer generated technology, which lends them the same overall feeling, 3D animation dominating the viewing experience almost completely. The plot is similar, in both cases humanity is at the brink of extinction and it is up to scientists to come up with solutions.
While I was watching Pale Cocoon, for some reason, I thought of this. I don't know why; it's a post-apocalyptic science-fantasy (nothing to do with Final Fantasy except being directed by its creator) about a scientist who is the host for one of the aliens that destroyed humankind. She believes that the way to banish the alien threat is to collecty seven "spirits"... well, I'm going to spoil it if I go on more, so... basically, I don't know why I think Pale Cocoon fans would like it, but I think you would. :)