I don't dislike any of the games in the series, but out of my least favorite:

IV: The story is obviously what it was all about in this one. Not just what happens, but how it's presented, the accompanying music, and the graphics. Obviously this is a classic.

VI: The dungeon design was ridiculous in this one, especially with the multiparty dungeons. I also love the cornucopia of unique equipment that allowed you to do so many things with the characters. Four equipment slots and two accessory slots may just scream "break me!" but I still adore having that level of customization in a game.

XIII: I really, really liked this game up until Gran Pulse. Law school meant I had to wait a few months to start the game so I could really dedicate myself to it, and at that point, I was able to push the lack of towns and lack of level design out of my head. I was able to just experience it for the entertainment experience it was, and it was glorious.

But the reason I liked the first chunk a lot better was because they limited you to only 2 or 3 party members total. Not only did this provide unique gameplay experiences for the battles but you also had unique character interactions which, when you have only two interacting with each other, allowed a lot more of the characters to shine through the game. I think I agreed with Loony BoB back in hatefest spitstorm that was the XIII Backlash Era, that these seemed like the most fleshed out characters in any FF to date. I think I still stand by that. But when you got to Gran Pulse, the party was really together, and at that point you realize a couple of things that kinda showed how deficient the game was, which I'm not going to get into because that's not what this thread is about.