Which final fantasy in you opinions is the most expansiv and fun to play game.....and which game do you think has the most extra things you can do after the game is over, and if your posting to help me out than i rate the importance of extra things like this in following order.

Extra optional bosses
Hidden summon monsters
Hidden weapons/armor
Sidequests to beat for game reputation
hidden scenes and movies and strylines

I have currently beat most the final fantasy's and am looking for a version to dive into for its playability past the end of the game....So far i am thinking number 10