Musings du Jour. One of the things I'm slowly figuring out as I work on and research the genre for Beauregard is that crime writers like details. My guess is that it gives the detective narrators that little ping! of veracity, the one that says, "This isn't just a story, it's a dossier, or a witness's report for a court case." This may be one of the few genres that it's appropriate to give flat-out descriptions of people. So you can turn them in to the cops. Or at least have the option.
Whereas a straight fantasy story doesn't require meticulous physical descriptions with the introduction of the character, and is, in fact, a big turn-off. "He was a tall, blond giant of a man. His muscled rippled in the stiff breeze, and his sword...well, it was still in the sheath, but let's say it left a big bulge." No, with fantasy, you're supposed to suggest the physical characteristics of your little roleplayers by the way people respond to them. Or you can give their histories, the history of their races, a description of their homes. You might be able to get away with a physical description if (and only if) the physical description describes the choices they've made that reflect in their dress, bearing, etc.
"Bilbo Baggins was standing at his door after breakfast smoking an enormous wooden pipe that reached nearly down to his wooly toes (neatly brushed)--Gandalf came by. Gandalf! If you had heard only a qharter of what I have heard about him, and I have heard very little of all there is to hear, you would be prepared for any sort of remarkable tale." -- The Hobbit.
"The man's tie was orange as a sunset. He was a large man, tall and meaty, without softness. The dark hair parted in the middle, flattened to his scalp, his firm, full cheeks, the clothes that fit him with noticeable snugness, even the small, pink ears flat against the side of his head -- each of these seemed but a differently colored part of one same, smooth surface. His age could have been thirty-five or forty-five." --Dashiell Hammett, "Too Many Have Lived."
Other genres? I don't know. The sci fi that I read tends to cross all sorts of boundaries, so it's hard to generalize. I don't really read much straight fiction, although...let me check a particular favorite:
"'When your mama was the geek, my dreamlets,' Papa would say, 'she made the niping off of noggins such a crystal mytery that the hens themselves yearned toward her, watzing around her, hypnotized with longing. "Spread your lips, Sweet Lil," they'd cluck, and show us your choppers!"'" -- Katherine Dunn, Geek Love
(Sorry about the over enthusiastic quotation marks. When I was a kid, I'd write letters like this: "Hi -----. Well, I don't know much. See ya, DeAnna. P.S. ..." and thence would follow the actual letter, each topic gaining another postscript.
Yup. I've been annoying my whole life.)