I just thought I mention new speculations mentioned by other guys/myself in this thread, saves you from reading every page of the latest ideas of how this fight went down courtesy of the events shown of how the forth hokage managed to stop the nine tail fox.
We found out recently Mito sealed the fox within the herself, how or when is unknown. Maybe this happened during the fight similar to the forth hokage's encounter. This at the very least takes the fox out the equation leaving the first hokage and Madara to duke it out. I highly doubt Mito wouldn't have been then able to fight using the fox then and there after the sealing. Why you ask? Look how long it took Naruto to control the fox, to think Mito would have been able to do it then and there then start fighting seems way to far fetched. I guess a flashback like the one we got for forth hokage would tell us for sure. Which by the way I think will come because it would add to the story as we would find out how Madara survived, if tobi really ends up being Madara that is. http://www.narutobase.net/manga/Naruto/500/5
Another possibility is the first hokage completely halted/paralyzed the fox similar to that seal Yamato placed on Naruto as he entered 6-tail form but obviously a lot more powerful and disabled the fox from intervening with the battle and then it was sealed within Mito.
Once the fox is out of the picture this still leaves another challenge, Madara. Originally we thought time-space techs were only used by the Forth hokage, then saw Tobi(most advanced one to date) use them and now we know that the 2nd hokage can use similar time-space techniques as well. So this begs the question, do you think the first hokage knew space-time techs as well?
There's a element of the first hokage were not looking into too much, you guys recall the Scroll of seals, written by the first hokage(the one Naruto stole in the first chapter) well I notice there's a scroll with striking resemblance in the picture where Madara and the fox are faced off against the first, could it be the scroll of seals?
Maybe on this scroll there's time-space techs or for that matter other ridiculous techniques that make the shraingan techniques look average?
I think little by little Kishi is showing us how powerful the Senju clan were back in there Glory days.