Saying this is better than, or an improvement of Square Soft's Final Fantasy: The Spirits Within, is not something I could possibly say (after all, FF:tSW actually caused Square to go backrupt

The CGI used is wonderful. It does not have the crisp visual that Spirits had, however, action sequences are done much better in here, as it is fast paced. So the overall presentation of AC is wonderful, with excellent detail.
The story line is wonderful, however, it is more so if you were a follower of the game. While you can watch and enjoy this movie stand alone, there will be a definite increase in enjoyment if you played (and liked) FFVII. The DVD includes extra material that does a quick run down of the game in attempts to get you up to speed with the movie. The two people I showed this to who had not watched the game very much well enjoyed this movie.
The sounds are excellent. Music from the game can be heard redone throughout the movie. The movie has its own music as well, and it blends in well with the remade original music.
Overall, this movie is wonderful. It is possibly my favorite animated film ever. Great action, compelling story line, wonderful music and score, and characters who can grow on you (and already are grown on you if you played FFVII). If you do anim