Kishi is a big fan of balance/"opposites attract" sorts of pairings / relationships. Often he'll use a yin/yang metaphor in there to really drive the symbolism home. Hinata is basically the thoughtful/reserved type, like Sasuke (non-insane Sasuke anyway); to Kishi, this makes her perfect for Naruto, who is more passionate/impulsive. The fact that Hinata comes from an elite clan of Doujutsu users just adds to that. Likewise, I believe Uzumaki Karin is the end girl for Sasuke, for the same reasons: she is the yang to his yin, his "female Naruto."