Budokai Tenkaichi 3 will indeed be VERY missed. Best anime or manga based video game of all time, in my opinion.
However, in all fairness, Battle Of Z is decent. It's not revolutionary or unique by any stretch but at the same time it's not bad in any sense. Battle Of Z is much like the racing game Blur... it's tedious and boring if play on your own, but play it with at least half a dozen other people, or better yet your friends, and it's absurdly entertaining.
Personally, I think most video games based off of Shonen anime or manga tend to suck in general. Dragon Ball Z, Naruto, Bleach, Saint Seiya, YuYu Hakusho, Fist of the North Star, Toriko, Hunter × Hunter, Fairy Tail... even ONE PIECE produced a few stinkers in Pirate Warriors 1 & 2. I mean those games were the epitome of button mashing. As far as I know, only JoJo's Bizarre Adventure has come out mostly unscathed when turned into video games.
Here's to hoping that J-Stars Victory Vs will be awesome but I'm still skeptic.