No 'XIII' title plays the same as the other. It's better than having each title have their own numeral (in which case we'd be in FFXXIII or something at this point). Name sells, and this is better way to do it than keep stacking the numbers.

If the games were mere copies of each other in most aspects, I'd agree. But all they have in common is parts of the lore (which is expansive enough to last for many games). Horrible.