Bingowings said:
At no point do I stop believing in the characters in ANH and ESB and a lot of that came from very good casting (Lucas himself has admitted to not really being an actors director).
Even in ROTJ most of the time the original cast and Ian McDiarmid manage to pull it off even without help from the directors (Marquand and Lucas by most accounts).
I'm pretty sure GL had ESB and RotJ ghost-written.