Uchiha Sasuke hates Uzumaki Naruto.
He hates the way he can be so cheerful in the face of total adversity. He hates the way that he tries to be his friend, and can't see that he needs nothing but his revenge. He hates the way he is so weak, and will never be a worthy rival to measure his own power against. He also hates the way that Naruto grows strong, and the way he can't seem to grow in the same way. He hates the way Naruto is special, because it attracts That Man's attention, when his only goal in life is to kill That Man. He hates the way that he takes nothing seriously, except his promises. He hates the way that he can make a promise so lightly, but doesn't know how easily they are broken in this world. Most of all, he hates the way that Uzumaki Naruto constantly proves him wrong. Uzumaki Naruto always fulfills his promises.
Uchiha Sasuke admires Uzumaki Naruto.
He admires that way that he always gets up after falling down. He admires that way he can stand proud after failing a thousand times before getting it right. He admires Naruto's ability to remain sane in a lonely world that hardly has a place for a poor, annoying, clanless orphan. He admires the way he can make friends without exchanging any words. He admires the way he gives everyone a thousand chances to become his friends, and tries his hardest never to allow them to become his enemy. He admires the way he can take on the world, believing in himself, his friends and his values and come out victorious in the end.
Uchiha Sasuke relates to Uzumaki Naruto.
They knows what it's like to have no family. They know how it feels to live in a place you feel you don't belong in. They know what it is to feel alone, completely cut off from the world. Uchiha Sasuke thinks he and Uzumaki Naruto know the darkness. He believes they both still live in the darkness. But Uchiha Sasuke can't relate to Uzumaki Naruto in that way, because Uzumaki Naruto found his way out of the darkness, and became the light for others to follow. Uchiha Sasuke is still trapped, because he allows himself to be trapped.
Uchiha Sasuke loves Uzumaki Naruto.
He loves his radiance, and he loves the way he gives him small glimpses of the light. He loves the way that, even when beaten down, he will extend his hand to another, heedless of himself. He loves the way Uzumaki Naruto looks at him with such vibrance and excitement. He loves the way he is infectious, and reminds him what it's like to smile and laugh. He loves how he distracts him from his horrid world and lets him forget about his pain and vengeance. He loves how he can cure him of his poisonous hate for a short while, and replace it with some of his joy. He loves the way that he will allow him to lean on him when he needs it the most, even if Uzumaki Naruto doesn't know that he's cracking through the cold, carefully sculpted mask of Uchiha Sasuke.
Everyone knows that Uchiha Sasuke hates Uzumaki Naruto.
But it's only for show. And only those two know it.