The biggest effect Julius Caesar had on Rome was his transform Rome from a republic to an empire. He also updated the Roman calendar, was undefeated as a general, alleviated the taxes of the working class, significantly expanded Roman territory and invented the newspaper. He also instituted the reign of Caesars.
Julius Caesar was a great military general who, after having been removed from his governorship of Gaul by the Roman senate, staged a coup and took control of Rome by force. He then defeated Pompey, the person with whom he was once aligned to take control of the empire. Although he is often portrayed as a tyrannical dictator, Julius Caesar was somewhat of a champion of the people. He eliminated the heavy taxes levied on farmers and granted any Roman citizen with three or more sons land. He also made the dealings of the Roman senate public by posting an account of them for the public to read and realigned the Roman calendar to coincide with the seasons. He also declared himself ruler for life.
Since his lineage could be traced to the founding of Rome, the role of the Caesars came to be associated with the role of the gods, who had more power than senators in the eyes of Romans. All of these actions infuriated the senate, which felt that he had compromised its power. This ultimately led to the senate attack on Julius Caesar that killed him.