Parker goes well with Whedon and the X-Men in part because Spenser and Hawk have always been superheroes in noir drag (the strongest, pure of heart, etc.). The humorous/gritty erudite-but-slang-savvy voice derives I believe from the 20's in general and H.L. Mencken in particular. The hard-boiled tradition dates from the same time I believe, as a reaction to WWI.