Hello, Fellow Vizzed users! Today I'm going to make a guide on how to unlock Broly and Hercule. 

  So first of all, lets start with Broly, because he is pretty easy, So first of all, to unlock Broly,
You must be playing Goku's Storyline. At buu saga, Before Potara fusing with Vegeta, On the
Map there will be 2 Red points on the map. You have to go the one in the middle, of the map,
Supreme Kai (As Goku calls him, he is actually Kibitoshin lol) Will sense a power level that
is more wicked than Majin Buu's. So after this is simple! Finish Buu Saga! After finishing kid 
Buu, Cutscene will appear, After that The Legendary Super Saiyan, Broly, Defeat him to unlock.
BUT! You have to Finish Goku's storyline once to make him appear! 
  So we move on Hercule! For this, You have to beat Piccolo's story once. So, While you are 
Playing Piccolo's story for the second time, At the part where you will get to the red point
Named "Sky" Enter, After that go to desert , you will find hercule training there. After talking,
Go to Central City, You will get Hercule as a playable character.

Hope I helped! I might do more guides about this game since I love this game See you!

I actually own all the Budokais on PS2, so should I grab the HD Collection?

   I actually much prefer the Budokai Tenkaichi series better, but some of the alternate stories and some special attacks were WAY cooler in the Budokai games. Like, in Budokai 3, Bardock's Ultimate, he hits the enemy, and his friend's pop up, as he's putting everything into his attack in their honor, and then he punches the enemy, causing a massive explosion, and changing the battlefield. Then, in Budokai Tenkaichi 3, he throws a large energy ball... ... So, yeah.

   I've also been playing tons of Xenoverse. I think Budokai Tenkaichi 3 is way better, but I do like how you change fields to complete missions and the Create a Character is really fun. Hate the random loot drops system though...

  They actually used new soundtracks mixed from DB Budokai Tenkaichi 2 and 3 for Budokai HD Series, Which I think is pretty cool and I really enjoy the music. The bad thing is, Budokai HD Series didn't include Budokai 2 in it, only including 1 and 3. The graphics got improvement, and they improved it alot it looks pretty good.
  Actually like you said, I like Budokai Tenkaichi too, I liked the gameplay alot of it. The transformations animation looked pretty good. I'd pretty grab Budokai Tenkaichi HD Collection if they do it in the future...