There is a lot of hate about this game that is highly unfair.
I honestly don't get it, since the only other games in the series that I have played were complex and I didn't feel were as thought out as well as this game. People should honestly start appreciating this game.
The major complaints I have heard of this game, was:
1. This game was futuristic, it isn't a Final Fantasy game, and
2. The game's theme song is by some pop star, and her song doesn't even fit the game.
Neither of those statements are fair or true. Yes, Final fantasy 13 was futuristic, although someone who has played the game would notice that while there are futuristic elements, the game still carries out a lot of aspects that were built into previous games.
Anyone who has seen the trailer with the theme song playing, has heard complaints of the song not fitting in the game. Yes technically the words don't reflect scenes in the trailer, but if you bothered to actually get to the end, you might find that they fit the ending.
The games battle system was outstanding, it really shone for me. It was fun, exciting, and very easy to get used to. It was exceeding that of Final Fantasy 10 and 12's by far.
This game in some ways may turn out like Zelda: Twilight Princess... as a matter of fact, this game may have done everything better than the other games of the series, but people won't appreciate it.
Final Fantasy games are known for their strong stories and beautiful cutscenes, well this game had all that and more, it's voice acting was done a lot better than previous games, the characters themselves were interesting and the development of the story throughout was amazing.
The graphics were nothing to be amazed at completely, this is again like Twilight Princess, it was too realistic, the colours were somewhat "Muddy", but it was still beautiful, I am not saying that this is what other people think or say, but I believe that people are judging this game for the same reasons as Twilight Princess did.
I think that this game will eventually get praise from a mass of people, but for now I am so happy with this game, definately one of my favourites. Even if you aren't a fan of FInal Fantasy, you will likely love it. If you are a fan you might be disappointed... I don't know why though... ask the fans who trash this game.
Honestly, this game is EXTREMELY underrated by many people.