I watched Coryn play through 13 and 13-2. He seemed... really guilty that he liked them. Like the way he said it, they were needlessly-complex in terms of story, really linear in terms of progression, and pretty limited in terms of combat options, but he still liked it for what it was. I can't say anything about 11 or 14 because those are MMO's and that kind of poisoned the series for me.
As for me, the last objectively great numbered Final Fantasy was 9. If you're looking for a the best one of all, that'd be 6.
To be honest, the only good Final Fantasies still coming out are the spin-offs. The FF Tactics games and Dissidia FF actually tried new things, and pulled it off marvelously. I've also heard great things about FF Type:0, but that's Japan exclusive right now...