He only surpassed Itachi's use of ninjutsu, but Itachi was the most talented at genjutsu, it's symbolized with them both sharing Amaterasu but one having the more powerful genjutsu and the other having the more powerful katon ability.
Imo they both inherited a portion of Indra's power but as the transmigrant only Sasuke could unlock it with EMS (cause of the prophecy and shit). Sasuke had the stronger chakra and Indra's ninjutsu talent while Itachi had the superior intelligence and Indra's genjutsu talent.