I first saw James McAvoy in Becoming Jane, where I thought his performance far outweighed that of Anne Hathaway. Although it was fine acting, I simply didn't like the character well enough to really dwell on it. Not long after, I saw Narnia and was quite tickled by his emotive performance as Mr. Tumnus. He seemed so out of place and so much more alive than the other characters... After that, Atonement, and after that, Wanted.
All in all, I have to say that I think James' acting is some of the best I've seen in a LOOOOOOOONNNNNNNNGGGGGGGGGGGGGGGG time, if not all time. He is really believable in all of his characters, and much more - he is compelling.
His quizzical gazes in Atonement were enough to transport. He comes off the screen in more dimensions than film is normally given credit for.
He is a delight to watch and he makes even the most querulous complicated storyline easy, he is just that competent.
We are so lucky!