A well-done film version of the book, yes, but there are some obvious problems. But when has it ever been different? Any film of a good book always suffers by comparison. In some ways, we have to acknowledge this and expect a film version to be something less, but perhaps quite stimulating--particularly visually-- and hopefully, will encourage us all to go back to the books.
The Chronicles of Narnia is apt to be compared to the LOTR's films of the last three years and this is understandable, but unfortunate, I think. The books are not really comparable. Lewis was knowingly using a modern, children's genre of writing while Tolkien quickly moved out of the children's realm (The Hobbit) into adult fare as the black riders enter into the Shire.
The films, if authentic to the books, will contain the same distinctions at some level and should, in some ways, not be compared. To break my rule, however, the Narnia film comes in a weak second in character development. One does not care enough for the characters to really care that much about what happens to them. In the LOTR's, one cares much more quickly for those characters, it seems. Of course Tolkien's writing was much deeper and multi-layered compared to the Narnia series, so the characters are already embedded in many of our minds. Also, the LOTR's takes more time with each movie to accomplish its character development.
I just didn't care that much when Aslan was killed. I thought the scene where the witch confronted Aslan about the law was much more powerful. The centaur who was essentially the general for Peter's army gave, for me, the most sublime and eloquent picture of what Aslan was all about. When he saw Peter in trouble, with the witch's army closing down on him, he leapt to his aid and did just what he had said earlier to Peter that he would do: He would be with him "to the death."
That was good story-telling.
At the end of the day, a good film of a great book.