For M4, anything by Jepe. His two most recent characters--Kenny and Leo/Madoc--are my personal favorites. Mec4D also has done nice work--her Eli and Hunk characters are among my favorite standbys. Morris, too, though some of her older work is 3000x3000, I believe, and some of it has a slightly grainy appearance in closeups. BergieD's TAI has really beautiful textures, but the material set up is strange and requires manual adjustment if you're going to use something like EZSkin; no displacements but high-quality bump maps.

There are a lot more options for V4 and I wouldn't say I have a single go-to artist for her. One problem I've noticed V4 textures tend to have even over M4 textures is unfortunately a lot of baked in specular, but there are still plenty of nice V4 textures out there. Godin's work is beautiful, especially her Asian characters. PDesign is another good one. Surreality does good work, too, but is more stylized, which you said you didn't want. Silver also does nice work, but her textures definitely have an airbrushed feel. I've only bought one of Mihrelle's characters, but I was very satisfied with the quality of it--slightly airbrushed, but I prefer that to baked in specular. I don't think Mec4D has done more than one or two characters for V4 and I don't have them, but her M4 characters are fabulous, as I said.