Most Cited Philosophers (born since 1900) in the Stanford Encyclopedia of Philosophy

Here.  I'm a little puzzled by the omission of H.L.A. Hart, but perhaps that is right--a casual, but not careful, search suggests he should be on the list.

AN IMPORTANT CAVEAT:  It appears Professor Schwitzgebel did not look at historical entries, which surely depressed the total cites for philosophers like Hart (who is not on the list) and philosopher like Nussbaum (who are on the list).