I'll make a full list too.

I: nunchuks
II: character progression without experience points
III: jobs system
IV: the world, the moon, underground
V: gilgamesh
VI: story, music, villain
VII: chocobo breeding, gold saucer
VIII: space, an awesome city like Esthar
IX: monkey-boys
X: rikku's wetsuit
XI: community
XII: world (I've wanted an Ivalice MMO for awhile now)
XIII: voice acting (more of it)