I'm not saying that he's the best of all the different versions of Optimus, but after seeing DOTM, I can definitely say he shows the broadest range of emotions, both vocally and physically. All of the other Optimus' (Optimi?) seem to always be calm, collected, and almost saint-like. Movie Optimus has been happy, filled with rage, hurt (by Sentinel's betrayal in DOTM), frightened, and surprised. He really seems to be a lot more passionate, if anything.