Brian Weatherson, a philosopher at Brown University, writes with the following additional data on cites to philosophers at the SEP cite:

“If you do a search for David Lewis you get 80 mentions in 44 entries.
It’s hard to know how to compare this to other rankings, but here’s some other
searches for full names

Saul Kripke: 23-17
Hilary Putnam: 25-22
Ludwig Wittgenstein: 22-11
David Hume: 78-35
Gottlob Frege: 43-24
Rene Descartes: 43-21

I imagine that Lewis’s full name hits are higher simply because he had a
common name, but still by that measure he stacks up pretty well against
other people on the list. (I imagine he’s the most commonly cited
philosopher on the SEP who doesn’t have his own entry yet. Which implies
someone should write the said entry. Ted Sider maybe? Or Dean Zimmerman?)”