I will start with Nagato because to me he represent the other side of the Naruto coin. I feel like there are many people who will want to compare Naruto to Sasuke, or Jiraiya, or even Kabuto (yes I have heard this too), but the truth is that Naruto's other half should be Nagato. The reasons are in their backgrounds and power.
Nagato, like Naruto, is a direct descendant of the extinct Uzumaki Clan. He like Naruto was left an orphan at a very young age. Interesting enough, it was Konoha ninjas who leave Nagato an orphan. It was also the Leaf Village leader Danzo, who along with Hanzo, caused Nagato's second great pain, the death of his friend (and adoptive older brother) Yahiko. These two pains are what cause Nagato to lose his sense of compassion and show the world what pain really is.
Similar to Naruto, Nagato's main power comes from an unwanted gift given to him while he was very young. While Naruto received the Nine Tails, Nagato received the Rinnegan from Madara Uchiha. It was this gift that completely changed Nagato's life as it gave him the power to essentially be the most powerful shinobi in the world.
As a child, Nagato was almost the complete opposite of Naruto. While Naruto sought to be acknowledged and was mischievous and loud, Nagato was quiet and unsure of what to do. What they both believed though was that they needed to be the path to ending the suffering of the world. While Nagato wanted to follow the path of a leader who would lead to peace, Naruto sought to lead everyone to peace. While completely different in personalities, they both shared the same values and conviction to making said value come true.
These values and goals were further re-enforced by the teachings of the sensei they shared, Jiraiya. Both took on his will, and his skill. While Jiraiya dedicated his book to Nagato, Naruto's name was an homage to Jiraiya's book. While Nagato killed his former teacher hoping to end Jiraiya's beliefs of peace, Naruto kept his teacher alive in learning his combat style and completely defeating Nagato by stating Jiraiya's values and beliefs.
Nagato, to me, represented one of the saddest, if not saddest, characters in Naruto because he was destined for greatness. He was destined to be someone great, but in which way was determined by the wrong factors. While Naruto had his friends to restrain him from losing his conviction (and his parent's ghosts), Nagato lost everyone who would be able to bring him back from the brink.
The same path to greatness for both Nagato and Naruto, but they each one went a different way when they reached the fork in the road.