Burst Limit is like an awkwardly paced remake in Budokai 1. Raging Blast is like a simplified Bt3 with a few more attack options. Raging Blast 2 has a stronger combo system but lacks a proper stroy mode. Ultimate Tenkaichi has a screwed up for general play, but the story mode really feels like the DBZ anime.
Despite not having an story mode, Raging Blast 2 is an awesome game. Great soundtrack, lots of characters and the best gameplay in the Tenkaichi series. So if you judge the game for what it is (a fighting game) you can find a very good game. My biggest complaint is that it lacks GT characters, but it's not that big of a deal. But if you want a 2D fighting game you should get Burstlimit. It's a bit too short but it has amazing gameplay. It's basically an enhanced version of the Budokai games with some features from Shin Budokai. So even if it's short you will probably want to come back and keep playing the game (i actually ended up playing for more than 70 hours). The HD collection while good it lacks Budokai 2 wich is one of the best of the PS2 series and they changed the OST wich is bad news considering the amazing soundtrack this series has.