Hmm...very close race, but I have to say Aslan. Maugrim is friggin' awesome, but Aslan is just...Aslan (even though I think they could've done better on his voice).
I think the real reason I ADORE Aslan is 1.) He's so CUTE!

and 2.) He's like what I imagine Christ would be like if he took on an animal form (large, protective...and oh so fuzzy and delicious! I just want to run up and throw my arms around his neck and burry my face in the fluffy furryness of his mane! LoL!)
Not to say that Maugrim didn't rock out loud too - I'm also sad that they killed him...he was cute too. But he was evil. But, then again, every movie needs a cool evil guy and The Wolf Captain certainly fit the part!
But still...my vote goes to Aslan. Sorry Maugrim lovers!