12 Has the best ATB system
Too true. I find the story of X-2 massively enjoyable, and I think the all-female dynamic is very well done, not to mention it's more than entertaining from a gameplay perspective and the side quests mean something. And as for XII, it's just pure magic for me - gameplay aside, it's got perhaps the best story of any FF to date in my opinion.
I personally would give X the best story credit, XII can have the best gameplay credit.
Separate names with a comma.