in terms of "famousness"; how widespread their influence was and the extent to which their works have been read as part of philosophical studies, I think:

tier 1: Aristotle Descartes Locke Kant Hume

tier 2: Spinoza Berkeley John-Stuart-Mill Leibniz Hegel Wittgenstein Nietzsche Satre

tier 3: Foucault Chalmers Dennett Fodor Nagel Heidegger Husserl

In terms of "famousness"; how widespread their influence was and the extent to which their works have been read as part of philosophical studies, I think:

tier 1: Aristotle Descartes Locke Kant Hume

tier 2: Spinoza Berkeley John-Stuart-Mill Leibniz Hegel Wittgenstein Nietzsche Satre

tier 3: Foucault Chalmers Dennett Fodor Nagel Heidegger Husserl

I should also point out this is very Western-philosopher heavy. You could add Sun Tzu, Confucius, et al. in there, but while famous they may be less studied in general. In my college, for example, I didn't learn about any of those until I took a specific course on Asian philosophy. Even intro didn't cover them. I have no idea what percentage of people go out of their way to take those courses, or whether that divide exists everywhere else too, etc.