XIII was fun for the most part. I got a little bored after a while since the game was a straight line, more so than X. I might even try my hand at XIII-2 if I have the money and time, since it's supposedly just a bigger improvement.
My favorite FF is VIII though, I only played it this summer, but I got really into it.
I should get around to VII and IX though. I was never that big on the FF series, my heart and soul was too into Pokemon to care. [oh look, did I make a pun?]