My husband got me Final Fantasy Advent Children on Blu-Ray. I already have it on DVD, but the Blu-Ray edition has 26 extra minutes of footage (plus a sneak peek at Final Fantasy 13!). At first I thought "wow. 26 minutes."
Wow, those extra 26 minutes gave the movie so much more, and it actually makes sense now! So if you were disappointed in Advent Children, I recommend watching the "extended" version. It gives more background about what is motivating characters, and some other little gems. :)