Both movies have terrible traits for appealing to the movie going public. The Spirits Within was jarring to the eye. It was a motion-captured, live action wannabe. It was as if the movie had the worst physical acting ever put on film. The story was awful, but digestable and movie-like.
FF7AC doesn't have the visual problem of TSW instead looking much more stylistic and appealing, but it's story/characters is water thin and not fit for adults to sit through for two hours in a theater. I don't know how people think it was confusing. I've never seen the movie straight through in one sitting (for obvious reasons) and I understand it. It couldn't be clearer who the good and bad guys are, as well as general motivation. And there's no subtext whatsoever. Casual FF fans would have flocked to see it in theaters because they like the material, but I don't think that's enough to make it a blockbuster and the movie is almost unapproachable to the average viewer outside of visual stimulation. The characters are impossible to latch onto for the uninitiated with absolutely no depth, and the story is complete, left-field nonsensery. It wouldn't make sense to people that haven't played the games.
What Square should have done is either remake FF7 in movie form, or make a FF movie that has the story qualities of the games. Introduce interesting characters, develop them, show the conflict in their world, have them form a party, take on the conflict and throw in some drama. It would sell as an adventure/action movie. You can't take the exposition out and expect people to come running to pretty CG.
[edit] Just realized I bumped a four month old thread, lol. Was searching the forums and got sidetracked...