I did not play the original Dissidia beyond the demo, despite wanting to, though I am a fan of the Final Fantasy franchise as a whole. That being said, based off of my time with the game, it feels like Dissidia 012 will not be making converts out of those who are not already into the Final Fantasy series. On the whole though, those who are fans will likely enjoy it, but it may strike them as too similar to its predecessor.
"...won't miss the mark in appealing to fans of the previous game"
My starting point for the game, and the meat of the single player content, is the story mode. This mode is split into chapters which determine the player's character and have him/her wandering around the world map accessing gates that contain boards on which groups of baddies must be dispatched. The story mode seems to have more potential than it lived up to in my play time. There's a lot of promise to the idea of having characters from various parts of the franchise shoved together in various scenes, but sadly the scenes themselves are ultimately kind of dull and lack the care needed to reach the potential of such a crossover. The game merely takes one aspect of a character and tries to build most of his or her interactions with other characters around that one area. There could be more depth further in, but during my time playing, I didn't see it.
The gameplay side of story mode is similarly an excellent idea that can't seem to find its footing. World map exploration is a fun concept that the early segments failed to use to a significant degree. Due to the game's essential requirement to keep leveled, it isn't really possible for the player to skip fights on the major boards. I found much of my time playing Dissidia 012 was spent in an endless string of Manikin fights that didn't serve any purpose but to pad the length.
The rest of the modes are centered almost purely on fighting. Every character has two types of attacks, bravery and HP, mapped to circle and square respectively. Bravery determines the power of HP attacks, as those are ones that deal permanent damage. This creates a sort of tug of war effect as bravery attacks lower the opponent's bravery. It's a unique system and blends well with the over-the-top bombast the fights are striving to showcase. The fighting system puts a lot of emphasis on movement within wide open arenas and allows for many ways to dodge attacks. Sadly, this becomes largely moot when there's a level disparity between characters upwards of five. At that point skill goes largely out the window as one side will outweigh the other to such a degree that it's not really possible for the weaker side to fight effectively.
Dissidia 012 hangs on to many trappings of an RPG. Players are free to customize their movesets to a degree and have control over stat boosting equipment. The basic moves afforded to a character can usually get the player through most fights, so the whole system seems like an interesting addition rather than a substantial aspect of gameplay. Still, it gives a degree of personal control and there's always fun to be had in modifying a character's equipment and movesets.
The game's cast is an assortment that nicely rounds out the somewhat sword-heavy main cast from the original. These new fan favorites bring something a little different to the table. Tifa's close range beat-downs and Yuna's summoning illustrate this rather nicely. Sadly, I was unable to determine the precise mechanism by which to unlock characters at this time. Most unlockables are available in the PP shop, where players can spend the PP that is earned after every fight. I'm certain that there are more characters than I was able to unlock, but was not able to just yet. The overall amount of content is certainly impressive with a great number of environments, music, outfits and characters to unlock. In addition, a system not dissimilar to achievements should keep OCD players coming back.
Dissidia 012 is definitely a crowd-pleaser sequel. It plays it safe and likely won't miss the mark in appealing to fans of the previous game, but it fails to extend the potential reach it could have were it to try to turn fighting game fans into Final Fantasy fans. Those of you who enjoyed the first game will be able to pick this up on March 22 in North America and on March 25 in Europe. As an item of interest, the game actually contains Dissidia's complete story within it upon completion, so those curious about Dissidia would be best suited in waiting for this game rather than trying to play the original.