This is curious, Superman is stronger or was (Pre Crisis) stronger than all of them. In the JL/Avengers crossover Supes took Thor out, although the jury is out on that as Thor said he had taken his measure and next time would be different, this is plausible as it is established in MU that Thor always holds back most of the time when dealing with mortals, remember he is a "god".
So I am not so sure why they seemed to give thor an edge over supes but given the matter transmutation powers of the surfer, he could technically take them all out in the blink of an eye.
I agree however that Mjolnir's abiltity to neutralize and absorb nearly any source of energy or energy blast would give thor the best chance in a battle that was essentially a death duel.
I would bet on SS but Thor is one of the greatest heroes and the most noble of any Universe DC or Marvel.
And on that note i can only ask straczinski this one question, where is Thor, man, Thor should be back in time for world war hulk the summer I hope.