Myth Thor defeats Myth Hercules. Whether Herc is immortal or not does not mean anything because the Olympians could steal be injured to the point they might as well be dead or better off dead.
Physically it is hard to say who is stronger. Thor is usually regarded as the strongest of the Norse gods and the Norse version of either Hercules or Zeus depending on who is doing the equating. Both were supposed to be the physical embodiments of strength for their respective cultures.
Except it would never come down to a strength test. Thor would fight this like he does all of his fights. A single hammer throw that can shatter mountains tears through Hercules living him a stain on the Earth. Thor then goes home and drinks an ocean's worth of mead. I don't see Hercules being able to overcome the range advantages of such a weapon.