I've played all the main final fantasy games, and I liked every single one of them, from I to XII. Sadly XIII ruined it, but I DID like the fight system xD It's the linearity, uninteresting characters and story that disappointed me . Sazh was the most interesting and real one, but Vanille was probably the most annoying character in the franchise history. Lighting was so so and Snow was at times interesting and then he'd become a nuisance. (I had to look up the names in wikipedia, I don't really care for these characters ). Also, who were the villians? I can't even remember!
I already have FF XIII-2 but I'm not in the mood to play it yet, I guess I lost all faith in Square Enix...