With the exception of Brutus? What? Brutus is the worst of the lot of them. A self-regarding idealist with absolutely no practical sense who - over-riding logic, Cassius, and everyone else simply because of his own faith in his own judgement - gets every single decision he makes in the play wrong. Brutus is the most selfish of the lot of them: so selfish, in fact, that he effectively believes himself some sort of demi-god, incapable of error.
I believe Shakespeare leaves JCs true characteristics as inscrutable and devoid of an objective definition. The major point of the play is the question of whether his murder is justified. He is both cruel and loving to his wife. He is stoic and accepts the will and prophecies of the gods yet defies and says he is stronger than danger itself.
By Act IV all other characters are shown to be selfish, conniving or lost, with the exception of Brutus. Is Antony any better than the worst that Ceasar might have been? is Cassius anything more than a jealous opportunist? It is the nature of politics to present a subjective spin on objective facts to an audience. Shakespeare is best in that he leaves JC's true character a provocative lacuna onto which the reader and characters project their interpretations.
I would compare Julius Caesar to a modern day dictator that people wish to assassinate for the good of the people/society. You could should how this modern day dictator has risen to power, how they rule, and why people want them out of power. What is the only way to get a dictator out of power?
Historically: "Caesar’s ultimate success as soldier and politician rested in his abilities as a general and his statesmanship toward defeated enemies. Julius Caesar was related by marriage to the great military innovator Gaius Marius. He formed a compact (the First Triumvirate) with Pompey and Marcus Licinius Crassus. However, Caesar could not overcome Roman aversion to one-man rule, and on the Ides of March, 44 b.c.e., he was murdered by his ambitious opponents. (Do some research, you will find many individuals had great impetous for murdering Caesar...some had no relation to his governmental desire for power.)
Within the play: "One of the most controversial issues surrounding the character of Caesar is the question of whether he was a good or bad leader, and whether or not his assassination was justified. There is no clear answer to this question. Caesar has been interpreted in a number of ways: as superstitious and weak, as ambitious and arrogant, as a commanding leader concerned with the well-being of Rome. "
I believe Brutus was selfish in that he made choices that benefited only him. He had a very twisted perspective on what he perceived as dangerous and harmful. It was his own quest for power and jealousy towards his closest friend Caesar that he plotted to murder him. Of course, he would have to blame the conspirators for influencing him to do so and the fact that he was concerned about a "perfect Rome." Brutus was a poor example of a faithful friend.