I am going to go out on a limb here and say Hercule Poirot, although an interesting character, never seemed quite like a man to me. Christie dodged it by making him "foreign" and full of tics and oddities that kept you from noticing that. She also had plots that kept you involved enough to not care. . I am sure some of you will disagree.
I think Elizabeth George does a great job with Inspector Lynley. Also Kate Atkinson with Jackson Brodie and Ruth Rendell with Wexford. Who else writes a believable male?