First off, the FF 12 has a completely new battle system. You do not need to cast the same spell over and over in a battle anymore. I find that this new change was a bad one. It takes away the player's involvement from the game since you can just "program" your character to make certain moves at a certain point during the battle.
The world map is gone, which was a very idea. Y
The graphics are nice and realistic. However, they are not very "Final Fantasy"-like. You can hardly distinct one character from another. It also doesn't help that there is VERY little character development in this game. The game mostly focuses on a political story. However, during much of the game nothing really actually happens! Last, all the characters are almost generic clones of each in terms of abilities and stats. They have stepped back in 5 years with EVERY character being able to do the EXACT same things with VERY minor base stat differences.
The music is not as good as in the other Final Fantasy games. Disappointing to say the least. It's not their fault though, considering that Nobuo left their team.
Overall, Square tried something new and failed. The music is bad, the graphics are bland and boring, the plot is bland and boring, lack of character development, lack of involvement. I could go on and on.