What past FF is your favorite ? What did you like the best about it ? What made it better than the others ?
Past faves: FF7,8,9,10 and to a lesser extent 6
Reasons:
choose who is in your party,
choose to do many side quests that are not just more battles
do puzzles sometimes
hunt for best weapons that you have a good chance of getting without the need for a guide
Miniquests that are fun and to find new secret areas
world map in 6,7,8,9
Use Summons in battle that actually help you out, and in X, use the summons as new battle characters.
Return to all areas of game, often for more quests or Monster hunts.
Traditional towns that break up the monotony
choose options in battle which are fully customised
select all allies in battle
use enemy skills or other game play elements in battle
Story and character development which is decent and for the most part well written
There are far more points to make but to sum it up, 6,7,8,9,10 are light years ahead of 12 and 13. The newer Final Fantasy games take choice away from you, they take gameplay away from you and they have lazy storytelling and graphics as a substitute for intelligent game design.
These are not good things. They are game flaws. Serious ones.