Base sharingan user can be consider kage level and suitable to be hokages.
Kakashi have only Halve on the uchiha eyes and he was well known for copying 1000 jutsu.Kakashi have almost all the element jutsu because of the sharingan.
base Sasuke take down dediara and orichimaru ,who were consider to be very powerful.Sasuke was even strong enough to take on itachi with kirin.
Itachi did take down Kureani and kakahi with base sharingan
Sasuke went through lot's of training to reach where he is now, but it was also clearly mentioned that Orochimaru was sick and weak and Itachi wasn't trying to kill Sasuke but Sasuke was. In the case of the fight with Deidara Sasuke was out of Chakra and was backed into a corner. Sasuke didn't win, he escaped (ran away).
Current Sasuke is powerful but he is swayed by his emotions and lacks the battle experience and the skills necessary to be on Kage level
In the case of Itachi beating Kurenai and Kakashi. Itachi is faster and stronger than Kurenai so of course he got her. In Kakashi's case Itachi did not use base Sharingan, he used MS: Tsukuyomi on him.
But I can say that Itachi is close to Kage level, maybe he even is Kage level. Not only because of his ability with the Sharingan, but his speed and power and mastery of the fire style technique. He has Battle experience and quick thinking. 'Cept now he's dead :shrug: