How do Brutus, Cassius, and Caesar resemble people in power today?
The brilliance and enduring quality of Shakespeare is that the tales he tells through his plays transcend his own time -- the themes are still applicable to our own, 400 odd years later. Although there may not be a direct mapping to the characters as listed to current day political figures, certainly the some parallels can be drawn. Throughout history, there have been leaders or rulers who overstep their bounds and accumulate as much political power as they can. There have been those who have responded to such threats with a sense of patriotism, to do the right thing for the sake of the country. There are also those who would do the right thing, but out of a sense of hatred for the usurper; in each of these, you can find the characters of Caesar, Brutus, and Cassius. Unfortunately, as more and more political power is concentrated into one individual, at some point they become "above the law" and act in their own interests, and not in the nation's, and undoubtedly have disabled or eliminated any opposition to them.
For a bit of a modern parallel, consider Hitler as Caesar. Those of his generals that attempted his assassination (there were actually many planned attempts on his life) realized Germany was losing the war and that he was no longer "good" for the country; and since there was no legal process to remove him, they resorted to assassination. Among them, assuredly, where those who just wanted to see him dead, and didn't necessarily care about what happened to the country.