"No writer was more competitive, or ambitious, than Mailer, author of such epics as 'The Naked and the Dead' and 'The Executioner's Song,' and critics would likely hand him the prize for his generation. But if sales are the measure of the public's mind, then honors clearly belong to
Vonnegut."
***
Sensibility also matters.
"First of all, Vonnegut's funny, and humor has a broad appeal," Gioia says. "Secondly, he worked in genres like science fiction and political satire that have an enormous appeal to boys, and boys are the ones usually reading Mailer and Vonnegut and those authors. ... Vonnegut was a very open and inviting author, less conspicuously literary than Mailer or Styron, although clearly a fine writer in his own way."
I tried reading Mailer. I never got far.