Itachi's the strongest uchiha after madara. even stronger than obito as obito had hashirama's cell and madara's support.
In the village obito was just a sucker! while itachi was at peak in the village and was able to kill every single uchiha (except his brother). Sasuke was nothing compared to itachi even after training with orochimaru. itachi could have defeated sasuke if he wanted to. And he is more brainy too!