Augustus shouldn't be mentioned next to Caesar, let alone Alexander. Caesar conquered Gaul, then crushed the Republic and his main rival. Augustus reign as emperor was impressive, before that he was less than impressive.
He never acted, he was a cold calculator who probably never even lifted a gladius in his life. Augustus sat back watching how others won his battles for him and watched how his main rival self-destructed. Then he conveniently took the throne after ensuring everyone who wanted him dead was either bribed, bullied or assassinated. That he later evolved into an old, demure grognard who banished his own wife and daughter is only irony.