Jane over at Dear Author did a post comparing 50 Shades vs Masters of the Universe (the fanfic which spawned it). It's a great post, especially when you take into consideration what the publisher has said about it.
“It is widely known that E.L James began to capture a following as a writer shortly after she posted her second fan fiction story,” Vintage said in a statement. “She subsequently took that story and re-wrote the work, with new characters and situations. That was the beginning of the ‘Fifty Shades’ trilogy. The great majority of readers, including fan fiction aficionados, have found ‘Fifty Shades’ deeply immersive and incredibly satisfying.” - from the Washington Post articleAt the time of this post, there's a lively (and currently wank-free discussion) about the comparison, the ethics of 'filing off the numbers' of a fanfic story and repacking it for profit, as well as the 'transparency' of publishers. Go check it out.