To me personally unless it is a CCG game now the turn based combat system hasn't really aged well. At least for some games like the older Final Fantasies. However I'd be remiss to not say which game I think had the best. Unless it was on page 2 no one mentioned Pokemon. Think about it. It combines collectible creatures with different attributes with Rock, Paper, Scissors. I consistenly call Pokemon "The greatest game of rock, paper, scissors ever." I think because of this, how easy it is for children to get into (don't lie. Most of you like me started when you were about 7-10 years old), and the added depth of the EV points makes it hold up better than most. The EV training is for the guys who I personally think take the game way too seriously but its there for them to do while the traditional leveling and rock, paper, scissors stuff remains for everyone else. So yeah to me Pokemon has the best. I also think its a game series that is a true testament to formula with how strong its still going and how long it has been around.
Also I was actually surprised, pleasantly so, that the OP thought that FF XIII had the best turn based combat system. The reason being is because, like the Star Wars prequels, I can find nothing but bile and scorn and related to it. Though I will have to agree with the other posters. It is Active Time Battle system. Though I do think its a good system and a good way to progress something like VII's or VI's outdated turn based system.
Also I was actually surprised, pleasantly so, that the OP thought that FF XIII had the best turn based combat system. The reason being is because, like the Star Wars prequels, I can find nothing but bile and scorn and related to it. Though I will have to agree with the other posters. It is Active Time Battle system. Though I do think its a good system and a good way to progress something like VII's or VI's outdated turn based system.