I saw one still of an older Anakin Skywalker in Episode 3. You could SEE the transition to Darth Vader in his eyes.....Creepy stuff.
They probably morphed it in there. Wooden Christensen has only the ability to emote one way, and brooding generally won't carry a picture.
Unfortunately, Natalie Portman seems to have picked this up from him, instead of spreading some talent his way.