> Who is the greatest contemporary philosopher that comes to mind?

That is a question that is as difficult to answer as "Who is the greatest contemporary scientist?"

Some candidates are Slavoj Žižek, Peter Singer, Annette Baier, Alastair Hannay, Daniel Dennett, John Searle, Simon Blackburn, Thomas Nagel, Leo Zaibert. The are also many famous philosophers are partly academics in specialist fields, eg. Richard Dawkins, Umberto Eco, Noam Chomsky, Steven Pinker, George Dyson and many more.