Wow, this is really pathetic.
Hey guys, how about we stop arguing about characters from flippin' books?! (Because neither is actually real!)
So what if "gandalf has magic and has alot of power"; so does Aslan, but they're both from books.
I hate to break it to you, but you can make your characters do anything when you write them; that's part of the magic of writing. So it's useless to argue about who's stronger!
For the record (because I love analyzing literature!), both characters are Christ-figures (both are resurrected; Gandalf is "the White," which is a reference to the book of Revelations; Aslan is the Son of the Emperor-Over-the-Sea; the list goes on).
I only say this 'cause it looked like some people were getting too involved, and starting to get their feelings hurt/enraged.