I always thought of Jaws as the "Original" USF attraction, simply because it is a huge part of the tram tour, and when they decided to do USF they want Kong, Jaws, and Earthquake to be their own rides. Jaws, and Kong for that matter, was one of the big reasons why USF even exists. It truly was hard to say goodbye to that.
Now, E.T. is the "Original" USF attractions because of the departure of Jaws, but if by original you mean an original USF ride that's unique to USF, it's gotta be the Horror Make Up Show. I could be wrong, but where else will you see this show at a Universal Studios Theme Park?