Any time there is a movie made because of a book being written, people always leave disappointed from the theaters. The book was such a huge success, in my opinion, due to the nature of the content and the high amount of detail given. Those details spark our imagination. Our imagination, as humans, is endless. A move will place limitations on that.
I think books are always better, the movies always cut out alot of the book to fit the movie into a certain time. I can see it all play out in my head, and the movies usually don't meet up to my expectations when they make them. They had a low budget and alot of problems finding actors so I say nope!
I think that books have more depth and understanding when compared alongside with movies and while movies aren't as time-consuming as the books, they have the ability to recreate a visual experience for the reader in a rather unique manner. Movies fail to achieve that and thus, it is often the case with movies that they cannot create and/or achieve the visual depth that the books can. In conclusion, while I think the movie may/will be interesting however, it cannot beat the books.
No, the upcoming "50 Shades of Grey" movie will not be better than the book series. Movies made from books are rarely, if ever, better than the books from which they are derived. Books allow the reader to utilize his/her imagination to create varying images in each reader's mind, allowing for a myriad of variations, whereas movies portray each character and situation just one way, and usually omit certain parts of the book.