I read Shakespeare's Julius Caesar as a play about perception. Whether Caesar is a monstrous tyrant or a sympathetic man depends on whether a person is a conspirator or not. From the perspective of the conspirators, Caesar is a monstrous tyrant who wants to be king of the Romans.
To the ancient Romans, the word "king" truly was a four-letter word. The Romans had driven out the last of their kings at the end of the sixth century BCE and a man named Brutus had helped them do it. Now, in the middle of the first century BCE, another Brutus aims to prevent Julius Caesar from becoming the first Roman king in 460 years. Thus, from the perspective of Brutus and the other conspirators, Caesar is a monster, who is on the very cusp of becoming king. Caesar may have refused the crown offered thrice by Antony, but the conspirators believed Caesar wanted to accept it.
On the other hand, after Caesar's assassination, Marc Antony's funeral oration makes Caesar look sympathetic. Antony argues that Caesar was not ambitious. Moreover, Antony argues that Brutus was practically Caesar's best friend:
For Brutus, as you know, was Caesar's angel:
Judge, O you gods, how dearly Caesar loved him!
This was the most unkindest cut of all;
When Antony reads Caesar's will, Caesar looks even more sympathetic because he leaves "seventy-five drachmas" to every Roman citizen and he also donates to the Roman people
all his walks,
His private arbours and new-planted orchards,
On this side Tiber; he hath left them you,
And to your heirs for ever, common pleasures,
To walk abroad, and recreate yourselves.
Thus, the question of whether Caesar is a monstrous tyrant or a sympathetic man depends on one's perspective. From the conspirators' perspective, Caesar was a monstrous tyrant. After hearing Antony's funeral oration, though, it is difficult not to sympathize with Caesar.