Well, in my opinion, Back To The Future needs to go. It's almost as bad as Body Wars was over at EPCOT. I couldn't go on either without either getting sick or bruised with all the sudden shifting going on in those rides. Granted, I was a HUGH Back To The Future fan back in the day, but times change. Besides, the Studios is getting a little outdated overall and a little change can't hurt. Just take a look at the E.T. Adventure. It's a great attraction too, but hopelessly outdated.
The Studios needs some need cutting edge stuff like Twister and Men In Black were for their time/addition to the park.