One of the most discussed questions from the anime. It is very hard to give an exact answer to this question, however, there are certain events or skills which proves that who is stronger. As the series name is based on Naruto, he is the strongest among the two. During the days when both were kids sasuke used to be the stronger because of his inherited uchiha traits.
On the other hand, Naruto was not that much strong. But he trained very hard to become strong. Once When Naruto was hospitalized, Sasuke along with sakura went to visit Naruto. There sasuke and Naruto started arguing as usual wich leads a to a duel between the two.sasuke and Naruto went to the terrace and started fighting there, both used their jutsu, Chidori by Sasuke and Rasengan by Naruto. Chidori made a small hole in the water tank and Rasengan almost blew it. It shows that Naruto is stronger. In adulthood, Naruto got full control over Kurama which allowed him to share his chakra with above ten thousand shinobi. He also fought with kaguya otsutsuki for incessant three days which shows how much stamina he has. Naruto’s destructive power is way too immense than Sasuke’s.
Sasuke has Sharingan and Rinnegan which allows him to be the wielder of the most effective Genjutsu, however, he can not put Naruto under his Genjutsu due to the Tailed Beast within him. Sasuke has the sussano, however, Naruto’s kyuubi mode can easily destroy that sussano. Sasuke has the teleportation technique but Naruto has so fast speed even greater than the yellow flash Minato. So if these two fight one another it is going to be a long fight and will end up as a draw or Naruto will emerge as triumphant.