I think both were the Chosen One, so either had the power to change the world but who would win between them was undecided.
Yeah I agree with this but I'll add a bit more; even the elder toad sage (big guy) said that the "Child of the Prophecy" did not refer to a single individual, but to both Nagato and Naruto who were trying to save the world. The fact that both Naruto and Nagato met was pure coincidence and unexpected in the foretelling, or that's the impression I got from both the manga and anime.
In regards to Minato, I think the fact he was Hokage means he could have done a lot more to change the shinobi world but the truth of the matter is he died young and he didn't have enough time, maybe down the road he could have but we'll never know for sure. Although even Minato could not come up with an answer to Nagato's question to Naruto during their fight just before he helped re-seal Kurama again, Naruto came up with his own answer using Jiraiya's teachings during his last confrontation with Nagato as we all know and able to bring Nagato back to the 'light' per say.
The 'Child of Prophecy' has evolved now to one who will bring the tailed beasts together again and set them on the right path, as the Sage of Six Paths foretold to the tailed beasts many years ago.
If you look at it like this, the three have changed the world in their own way:
Nagato -Possessed the Rinnegan, immense talent and through his actions in Akatsuki (capturing the tailed beasts), the shinboi nations created an alliance to counter the threat they possessed (7 tailed beasts), even Yahiko thought Nagato was a saviour before he died.
Minato - Was given Hokage role quite young, possessed immense talent and passed his faith onto his son to fulfill the prophecy during the Kurama attack. I guess you could say he was a pseudo 'Child of Prophecy' in way. I say 'pseudo' because as Hokage aside from protecting Konoha from Kurama, it seems that he did not achieve anything as Hokage but there is a chance he could have later on in life, if he had lived or that's the impression I get. The Fourth Raikage (A) also believed Minato to be some sort of saviour at some point until he died and 'failed', which makes me believe if he had lived then the Shinobi world might have been different due to the respect he earned among. The other thing is that Minato never believed himself to be a 'Child of Prophecy' and did not take on the role like Naruto did later on but believed Naruto would be the one.
Naruto - The current 'saviour', indirectly caused change to the shinobi world by being a jinchūriki of Kurama which has caused shinobi nations to create an alliance to protect him and the world from Akatsuki. He also managed to change Nagato back to the person he used to be before Yahiko died, which in term caused a dent in Obito/Madara's plan and changed several important people's way of thinking along the way including Gaara, Onoki and A. He has also gained the trust of pretty much 8 of the 9 tailed beasts, with 7 believing him to be the prophesied person that the original Sage of Six Paths referred to. He has also taken on the role as the 'saviour' without any questions and he has taken it upon himself to achieve the peace, his master, his pupil and himself want so he completes the prophecy more so than the other two.
I was thinking the same thing. Then one wild idea appeared. Madara could have been the child of prophecy. 
Or even Obito since they both have caused great change to the Shinobi world although the prophecy stated that Jiraiya would teach the saviour, so has to be Naruto/Nagato.
