The Budokai HD collection has a new OST. Just warning for any of you who loved the music from Budokai 3.
I played the demo of Battle of Z. It wasn't bad. I'm not sure how combos work though. It seems to be like Tenkaichi 1, where it's a 3 hit combo, 5 hit combo, get knocked down, get back up, etc. I couldn't get close range melee combat to work well enough. There's no charging energy, rather, your Ki is increased by simply attacking your opponent with melee, which is difficult enough, as I mentioned. The stages and character models look nice, though I'm not a fan of the lighting for most of them. The controls are floaty - I'm not even sure if I'm using the word right, so I'll jsut say that the characters, on ground, moved more fast and flimsy than one would expect. Also, rushing/flying to a character is a pain at times. Read this with caution, this could just be my ineptitude.
In terms of best DBZ games, man, I don't know. Budokai 3 is a great game in it's own right. I just which that some of the other weaker characters weren't given the shaft of having little to no attacks. But overall, it's a good game.
Tenakaichi 2 and 3 are great, and do a good job (moreso 3 than 2) of capturing the essence of the show.
I haven't played DBZ: The legends, but I assume it could be the best in terms of capturing the essence of the show.