This will be simple review till Dragon Ball Fusions comes out everywhere else (other then Japan)
Characters:
There are tons of characters you can play as in Dragon Ball Fusions, and thats not including all the fusions with those characters.
Game Length:
I haven't finished the game so far, and I've put 15 hours into it, but I have heard it offers at least 20-25 hours of story and it has tons of replayability.
Gameplay (Combat):
The Combat , as you and the enemy are in ether a Sqaure Arena, Circle Arena, Rectangle Arena and More, You have different things your character and team mates can do, 1 being a normal attack which does some damage to the opponent, 2 being a ki attack which again does more damage, and there are tons more things you can do like charge, super attack and even fuse. The Combat is enough to sell this game by its self.
Gameplay (Fusion):
You unlock characters and moves and more in story mode to build up your character (Who can then fuse with anyone, and that includes other Players) and then you can also fuse any other character in the game with someone, for example Broly + Trunks = Brunks and so on.
So is Dragon Ball Fusions good?
YES, Dragon Ball Fusions is probably one of the best 3DS Games to date and it has tons of replayability, I hope Dragon Ball Fusions comes out every where else soon and if it does I highly recommand getting it.
I Give Dragon Ball Fusions for Nintendo 3DS: 10/10