Ender's Game was clearly a great book. I enjoyed it a lot more than the other books the class read the year. One of the things that made it better than the other books in my opinion was that it seemed a lot more aimed at people of our age. Comparing it to the movie though is quite difficult however due to both the book and the movie being quite good.
My personal favourite of the two is the book though. This is usually the case when comparing book to movie not only with me, but with most others as well. Books are usually just plain better than movies, usually because the book is a brand new topic while the movie is just piggybacking off that topic, and in a book, your imagination can run wild whilst this is not the same as when watching movies.
There are some parts in the movie that they did a lot better than in other parts. For example, a good part that they did was how they represented and used the battle room on the movie. Another part they did well was how they created the battles that Ender fought. In my opinion, there wasn't any parts that they did really badly, and they kept the movie to a high standard.
The movie was quite good, but it wouldn't be the thing I would want to see again, purely because it is a movie I understand, as I only really watch movies again if they are really really good, or if I didn't understand the movie properly.