A short blog with my opinion about why the complaints about Final Fantasy 13 are unnecessary and even contradictory.
 
First off, the game is often said to be "one long hallway". Alright, fair enough, it is. But guess what? So was Final Fantasy X. Until you got to the Calm Lands in Final Fantasy X you couldn't go anywhere off the beaten path. Final Fantasy XIII is linear until you get to Gran Pulse, which is much larger than the Calm Lands. In addition, to those who complain about side-quests, Final Fantasy XIII has way more than Final Fantasy X did. Why do I keep referencing that game? Because everybody loved it, and it's essentially the same as Final Fantasy XIII when it comes to mechanics.

Complaints about the leveling system are also heard, but let's go into some more perspective. First off, the Crystarium is an -almost- exact copy of the Sphere Grid in Final Fantasy X, it just looks different. You can't stray away from your character's three main rolls until halfway through the game-much like you couldn't get off the set roles for the characters in Final Fantasy X until you got a teleport sphere or the like until halfway through the game.    
 
Not only this, but the leveling system is just a disguised version of the systems found in Final Fantasies I-IX. Each character has some sort of primary role they're supposed to be used for, so you must use them accordingly. There's no reason to complain about it being linear because it's always been that way.
 
The battle system is up for personal taste. I was getting sick of the old system, I see the new system as a welcome addition.
 
The story was character-based. This does mean a slower pace at the beginning, but everyone who's completed the game (or the majority of people) with an open mind will agree that it was story well worth playing through. I've read in forums "I lost interest in Chapter 10. The story sucked." The story will only suck if you don't complete it, it's like a movie where the ending puts everything that was happening in a new light and it makes you truly appreciate the movie. The ending (actually, last 10 hours) of the game brings all parts of the story together, and after seeing the characters grow through their hardships, you feel like you have completed an awesome task after beating the last boss.
 
The soundtrack has had no complaints as far as I can see, but it is quite good. It has probably the best boss music out of every Final Fantasy game (I'm saying it trumps my favorite boss music, Dancing Mad). 
 
The game is beautiful, but nobody can say it doesn't without looking like an idiot.
 
I think I've covered most major bases here. I would like to add that the game has a great sense of scale. But that's not what people look at.