Caesar is better known because of a couple of basic factors. First, he left behind his own personal writings in two books, the Gallic Wars and the Civil War. For that reason, his personality is more apparent. Caesar's works were available to western European elites throughout the Middle Ages, ensuring that he, as a personality, remained familiar. Augustus left no surviving literary legacy, and so his identity as an individual was left to biographers like Suetonius. In general, he is more difficult to access for the layman reader/researcher. Even in the modern world, a lot of the best scholarship on Octavian/Augustus is dense academic work from Germany and remains out of reach of the readers of coffee-table books on Rome.

This brings us to a second factor: Caesar's life was an insane and interesting story. He was a young, ambitious Roman aristocrat who formed the famous first triumvirate with Pompey and Crassus, had a raucous consulship in 59, and then went to Gaul to prosecute an adventurous war for the next 9 years. He crossed the Rhine, crossed to Britain twice, won many famous battles like at Alesia, and then came back late in 50 as a powerful and obstinate opponent of Pompey. His bold "crossing of the Rubicon" initiated a civil war which would span the entire Mediterranean and eventually change the face of the Republic forever. Then eventually he was assassinated in a memorable manner. He's a larger than life figure just by default. In contrast, Octavian was not an adventurer. He was not a military genius, he did not lead armies to the far corners of the earth, and his political maneuvers were more shrewd than flashy.