My favorites are, in order, Aslan, Lucy, Edmund, Peter, Reepicheep.
I love how they potrayed Lucy and Ed, Lucy being the one most faithful to Aslan, one thing I did really like is the films focus on the two's growing bond.

although, they kinda potrayed her as the gentle one... Susan...I really don't think was potrayed as 'gentle' at all in this one, although it did give her a bigger role....which is what Anna wanted.
And Ed was much more humble and thoughtful...you could really see his transformation, and it also made him much more likeable then in the first film.
I still love Peter...he was my 3rd fav char in the book and LWW....and...even though I didn't particulary 'agree' with his character change, I can understand why he felt and reacted the way he did, and it made his struggle to grasp the loss of Narnia as a full reality, much more believable....Lewis really didn't show much detail as to what the kid's reaction were to the dramtaic chance of events in the book as much as I think many of us would have liked, so I think this is just a "how they could have reacted" sort of thing...as everyone reacts to things in a different way....in this case Peter's bitterness got the better of him while Lucy put her child-like trust in Aslan even when things didn't make sence....although I didn't think it right that Caspian was older then Peter when in the book it was the other way around.... =/
And Reep..was just amazing!! Everything I thought he would be! XD