if you enjoyed XIII you should enjoy every single other iteration of Final Fantasy out there, even XII which i hated with a passion.
i hated XII but it was a quality game, XIII not so much.
if i had to rank the Final Fantasies i would rank them like this:
VI > IX > VII > X > V > IV > II > I > XII > XIII
my favorite game of all time is another RPG Chrono Trigger.
other noteworthy JRPG's are: Grandia, Suikoden 1-5, Lufia II
if you have the oppurtunity try them.