I believe there is also a Zoroastrian temple somewhere in America, but I can't recall where I've read this.
Anyways, I voted Jewish. If I were to lose faith in Orthodoxy, the only other Christian group I can possibly see as being true are the OO. However, if 'Orthodox' is to mean EO and OO, then I would go with Orthodox Judaism. The history of the Church leads me to believe that Catholicism, Protestantism, Nestorianism, etc. are all serious deviations from the True Church. If I were to ever join a Christian group that isn't Orthodox, it would be for reasons other than faith. And if I were to join a religion for something other than faith, I could probably pick a more interesting and free religion than some type of Christianity or Judaism, to convince myself of.