I've only played the first and second but out of those two, I'd have to say the second one was superior. The first game's list of characters was incredibly small and limited, while the second had a lot more choices.

If you've ever played Budokai (the DBZ games), they're very similar to those in that each new game is basically the same fighting system, controls, etc., just with new characters and moves.

So I'm guessing your best bet will be with the latest one.