Sasuke is Naruto's most precious person primarily because Sasuke was his first bond, because of their very difficult childhoods, and because Sasuke was the first Naruto's age to acknowledge him (granted Sasuke didn't say that, but he did train hard hoping Naruto wouldn't surpassed as far back as the Zabuza arc. that in and of itself would have be acknowledgement in Naruto's eyes)
Jiraiya and Izuna have more good acts regrading Naruto than Sasuke does, but Sasuke will always be Naruto's most precious bond. Naruto was willing to die by Sasuke's hand in order to stop him. Sasuke is more precious to Naruto then his dream to be Hokage. Even when Jiraiya told Naruto to give up on Sasuke, Naruto refused.
