I'm going to be among the few, here, with a contrary opinion regarding FF13. Honestly, I very much enjoyed it. While I admit it could definitely have used some editing to trim it up a bit(took me 85 hours total to get through the entire game, mostly because I spent a lot of time grinding levels and quests in the open world area), overall, I found the game to be a classically epic experience. It goes without saying that the graphics and cinematic scenes in the game were impressive, even breath-taking at times, but I also found the story to be one of the more complex that I have seen for some in an RPG.
My own interpretation of the story is that it was one centering around a theme of Free Will versus Divine Providence(WARNING: STORY SPOILERS AHEAD). The Fal' Cie are sentient automatons, but they lack Free Will. As it turns out, it's not just the La'Cie that have been given a focus; the Fal'Cie are the ones who were originally given a focus by the Creators(whoever they are; they never make an appearance in the game). The entire motivation of the story of the game is a complex plot orchestrated by the supreme Fal'Cie, Orphan, to accomplish one of two tasks, to either force the Creators to return to release him of his focus or to be destroyed by Ragnarok.Orphan was given a focus that he had to both protect and destroy the humans of Cocoon at the same time(during the end battle, Orphan reveals this with the quote "Too weak a shell, and they would not thrive; too strong a shell, and they would not die. Slaughter and salvation. Two irreconcilable focuses we bore.") You see, apparently, Orphan misinterpreted his focus and how to implement it, and had been struggling to properly fulfill it for the past so many centuries. He wanted to be released from his focus, but not having Free Will, he could not simply abandon his focus. So, he needed either the Creators to return, which he figured would happen if enough people start dying, or Orphan himself would have to be killed by his own creation, Ragnarok.
Yes, it turns out that Orphan was the one that created Ragnarok for the purpose of killing Orphan, and Ragnarok and Orphan have been fighting for centuries(we end up learning this, also, during the final battle when Orphan reveals his disappointment that Ragnarok still, after all these years, can not kill him). The reason is, because of his focus, Orphan can not simply let himself be killed. He has to be overwhelmed by a greater force, hence the reason Ragnarok has to be independently trained to have the power to defeat Orphan.
The party gets mixed up in this plot through Lightning's sister Sarah when she makes the request that the party has to save Cocoon and with the vague images impressing an unknown focus onto the party by the first Pulse Fal'Cie. It is later revealed by Dysley/Barthandelus/Orphan that Sarah was being used by Dysley/Barthandelus/Orphan to find a group that will be instrumental in destroying. Dysley/Barthandelus/Orphan also reveal to the party exactly what their focus is, since they seemed to be having so much trouble understanding it: to destroy Cocoon. Naturally, the party is appalled and struggle to find a way to overcome the focus without having to destroy Cocoon.
Like, I said, this is my own interpretation of the story, and I see everything that happens in the story, the creation of past La'Cie, the party's indoctrination as La'Cie, the struggle of the party against government forces, and the impending prophecy of Ragnarok are all orchestrations of Orphan to find a release from his own focus without violating his focus. Orphan has no Free Will, so he can not simply choose to let everyone die or to let himself be killed; nor can he simply decide to walk away from what he has been charged to do. He has to be overwhelmed, either by circumstances or a power greater than him. But, he couldn't simply create the situation in which this would automatically happen. There had to a good chance of it all failing, too. Orphan had to find a round-about way of setting things up without violating his own focus.
As far as the other aspects of the game, I found the battle system to be very fluid(if you actually took the time to really learn it and its various nuances, as opposed to just mindlessly pushing the one execute button, you would have found it's a rather fast paced and dynamic system) and the characters, unlike many prior RPGs, actually develop over time. Hope, while almost everyone despises him at the beginning for his whiny nature, changes to become the most mature and realistic-minded of the bunch, but you have to actually play through the game to discover this; although, Snow pretty much stays a douche from beginning to end. However the nature of his douchiness does change.
Many complain of the linear dungeon design, but the reality is that, topologically, we've been playing through exactly that same kind of design for years. We've just never noticed it as much because it was always curled up on itself. But, if you stretched out the design of dungeons in almost all past RPGs, you'll find that they are all linear paths with some branches to the sides. There are no multiple paths.
I will admit that the weapon upgrade system was a bit of a shock, but that was because it was something outside the traditional formula. I simply wasn't expecting it, so it was difficult to deal with, at first. However, after a while, I became used to it, and then it was much of an issue.
What I find most amusing about FF13 are all the people screaming that they were disappointed because it wasn't a FF7 remake, or it didn't harken back to FF7 enough. It's so humorous reading all the comments screaming for a FF7 remake(a game that is now roughly 15 years old) and wanting Square-Enix to not change the formula that was instituted with FF7; yet, I bet these same people are the first in line to complain that there is no innovation going on in the game industry.
FF7 was great back in the day, but that was 15 years ago. It's time to grow up and move on, folks. We have to find better, more sophisticated experiences as we proceed into the future. We have to try new things to expand beyond the same old tired formulae being iterated year after year.
ADDENDUM: Considering the release hit most people by surprise, I would think it's the lack of market that has lead to lack-luster sales, not disenfranchisement with the series.