Well... I've heard of Rousseau (possibly even had to read a little of him in high school?) and I hadn't heard of Algarotti until now :P Of course, some of this has to do with, well, the US being a Thing, which is hardly Algarotti's fault :)

I think that at least Candide is more read than Casanova's memoirs? If only because of Bernstein :) Though I can't argue that Casanova's name is better known than anyone else's!