Compare Macbeth and Banquo to well-known people in our world today. They cannot be fictional characters.
Hmm. A tough set of comparisons, actually. Do they have to be in the same country/ industry / discipline? It is easier if they don't.
How about Colin Powell and Banquo. Powell was a warrior, loyal in tough situations, and had predictions made about his future position (people said he could be president).
If we assume Macbeth's dominant characteristics are taking power he doesn't deserve, and listening to false predictions that shape his fate, how about Osama? He's following twisted predictions, killing those who don't deserve it, and doesn't seem to believe in his own death. (The problem there, of course, is that there's no Lady Osama/Macbeth.)
Maybe Kim Jong-il is better. There were omens at his birth, and so on.