In Julius Caesar, Shakespeare has all the major characters speak with a level of eloquence and beauty that the reader, or the audience, will tend reflexively to sympathize with them. For 2,000 years it has remained an open question whether Caesar was, as Mark Antony refers to him, "the noblest man that ever lived in the tide of times," or the despicable tyrant the conspirators believed him to be. Shakespeare's answer, paradoxical as it may be, is that he was both.
The courage Caesar displays is given a kind of supercharged validity by the words Shakespeare gives him:
Of all the wonders that I yet have seen,
It seems to me most strange that men should fear,
Seeing that death, a necessary end,
Will come when it will come.
Later, on the fateful day, he confronts the Soothsayer with the simple observation, "The Ides of March are come," and he is given an equally direct answer, "Ay, but not gone, Caesar." At this moment, Caesar becomes an everyman, for his situation is the universal one in which the future, at any given moment, is unknown to us.
In the Senate just before he is killed, Caesar does, on the other hand, express an almost childish boastfulness about his self-declared superiority.
I could be well moved if I were as you. . . .
But I am constant as the Northern Star,
Of whose true-fix'd and resting quality,
There is no fellow in the firmament.
But the language in which this is expressed embodies such nobility that it's impossible for us to reject Caesar's claims about himself. And then, his final statement before he is stabbed, "Hence, wilt thou lift up Olympus?" carries with it an apocalyptic quality, driving home to us, as readers or theatergoers, the immense tragedy of this assassination, and by implication, of all the similar political murders through the centuries.
Then, as the conspirators congratulate themselves after the deed is done, we cannot help seeing their side of the story. As Cassius asks, "How many times will this our noble scene / Be played again in states unborn and accents yet unknown?" It is Shakespeare's genius to make us see the complexity of life, in which there are two sides to everything, and no simple answers. And so, Caesar is a narcissist, but also a great man. And the conspirators—not only Brutus but the others as well—though they have taken the law into their own hands and committed murder, embody qualities both positive and negative, as we all do.
If I were you I would want to examine the imagery that is employed to describe Caesar and other characters' opinions of him, especially in Act I scene 2, which is of course the famous scene between Cassius and Brtutus. Consider the way that Cassius describes Caesar in these following lines:
Why, man, he doth bestride the narrow world
Like a Colossus, and we petty men
Walk under his huge legs and peep about
To find ourselves dishonourable graves.
Clearly, we need to remember that Cassius is deliberately exaggerating Caesar and his egocentricism for impact to help him in his purpose of enlisting the support and aid of Brutus, but at the same time, such images and descriptions greatly help to influence the audience. Let us remember that we have not actually seen Caesar ourselves, and so such images greatly help to influence the audience as to the character of Caesar. In particular, this image is particularly powerful in the way that it presents Caesar as a huge massive power that can barely be contained in the "narrow world." The way that Cassius describes himself and Brutus as "petty men" likewise helps to reinforce the central image of Caesar as being so powerful and narcissistic that there is no room at all for any other people.