When it comes to pride, Julius Caesar is the star of the show, as he's the most outwardly arrogant. Caesar's total lack of humility seems to be his tragic flaw. His prideful arrogance is a blinding force that prevents him from seeing the harm he's doing and the harm being planned against him. When Brutus is humble about what others call his greatness, he sets himself up in sympathetic contrast to Caesar. We like Brutus because he isn't all fatheaded. He also seems wiser than Caesar for being more aware of the world around him and genuinely more concerned for it.
Arrogance has a protective quality in the play: it's only by his intense arrogance that Caesar stays ignorant of the plot against him. Shakespeare points to arrogance as one of man's most dangerous failings. Under the influence of arrogance, a man can neither judge himself, nor accept the judgment of others.
Humility is a characteristic of the weak. Brutus lacks the strength and conviction to justify his murder of Caesar because he is too humble. If he had forcefully asserted that he had the right to judge Caesar, and the good sense to judge him correctly, he could have won the crowd over.