I cried actual tears of joy after riding Forbidden Journey for the first time, and I'm not even a hardcore Potter-nerd so I'd have to go with that as my choice. I've yet to ride the new Hagrid coaster so my vote might change on my next visit.
Just finished our first trip (a week before Hagrid's opened) and Escape from Gringott's was everyone's favorite ride - no contest. E.T. was actually the second favorite ride for me and my husband - children of the 80s unite! My youngest's 2nd favorite was the the Simpson's ride and my oldest's second favorite was Forbidden Journey.