I agree that the best Dragon Ball game is Tenkaichi 3. Budokai 3 was great for me, but it is more a traditional fighter and, except for the cutscenes and animations when doing super moves, the gameplay doesn't feel like the anime in the same way Tenkaichi 3 does.
The problem with Tenkaichi 3 is that it may feel repetitive because almost all characters play similar, and is a lot of button smashing. The good thing is, because it has like 140 characters, if you learn the moves with one, you practically learn the game, where Budokai 3 there were a lot of different combinations for each character to chain combos, and learn all of them would take a LOT of time.
I'm quite surprised your friends like to play the game and all. Most times I invite friends, they say it's awesome, but just too complicated to pick up and play. The tutorial is a most in this game.
I saw this videos and help me a lot to learn to chain huge combos. And I mean HUGE!, more than 100 hits in some cases.
Edit: Ohh, and the best anime game is the Wii Death Note fighting game... you know what I'm talking about 
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