Here is the resulting ranking:
1. Karl Marx [in a walk, apparently]Except for #s 1 and 10, this is a decent list, better than one might expect. It's not particularly informative, though, given the vagueness of "greatest." In coming up with my own list, I used more specific, if also subjective, criteria: points were awarded for influence (on me, past or current), present usefulness (again, for me), general importance, and other assorted intangibles.
2. David Hume
3. Ludwig Wittgenstein
4. Friedrich Nietzsche
6. Immanuel Kant
7. St. Thomas Aquinas
10. Karl Popper
1. WittgensteinHonorable mention [points awarded for: same as above, plus (if the philosopher is relatively new to me at present) estimated future usefulness]: Putnam, Rorty, Peirce, James, Isaac Levi, Robert Brandom, Dennett, Danto, Anscombe, Frege, Heraclitus, Zhuangzi, Kierkegaard, Hegel, Gadamer, Schleiermacher, Merleau-Ponty, Bergson, Jennifer Hornsby, Charles Taylor, John Haugeland, D. Z. Phillips. Okay, I'll stop now.
2. Donald Davidson
3. John McDowell
7. Gilles Deleuze
9. J. L. Austin
10. Stanley Cavell
Bottom five [using analogously subjective criteria]:
1. Colin McGinnAlso: Kripke, Husserl, Michael Devitt, Churchland(s)
2. Jerry Fodor
3. Ayn Rand [but see Dr. P's comments here]
4. David Stove
5. Jean Baudrillard
Opponents; that is, very good philosophers who are, in some important way, wrong, wrong, wrong, and helpful despite/because of their errors (see my earlier post about this phenomenon):
1. Barry StroudFor Sartwell's own idiosyncratic likes and dislikes, see here.
2. John Searle
3. Roger Scruton
4. Crispin Sartwell
5. W. V. O. Quine
6. Philip Kitcher (or Dennett in his specifically naturalistic moods)
7. Plato et seq.
8. P. F. Strawson (on some subjects)
9, 10. Descartes and his contemporary minion Thomas Nagel