Snoopy said:

I haven't played all of them, but my favorite is between 6 and 10.

I have played and beaten all of FF games from FF1-FF13 here is my list.

1.VII

2.IX

3.VI

4.X

5.VIII

6.V

7.IV

8.XII

9. III

10.I

11.II

12.XIII 

 

Left out XI as it was an online game and FFXV as I have yet to play it.