If you think about it the Fist Hokage had help. He wasn't the only one on the battle fighting Madara...................Mito (First Jinchuuriki of the 9 Tails)1st wins.
Nagato löose against naruto(i know at that time nagato was not helthy but naruto at that time use 70% sage mode n 30% kyubi mode/chakra). 1st beat madara and kyubi at the same time[madara with ems n full control on kyubi.and kyubi was also in it full open form at that time) and i'm sure that 1st surely know the secret abt rinnegen powers. So 1st wins here 4 sure.