Some readers interpret that Ran has known Conan is Shinichi all along and is just pretending to not knowing because she thinks that he has good reason for not telling her.Each deals, subtly or greatly, with culprits that either threaten to or are genuinely at risk of suicide, and each reflects a slow difference in how Shinichi deals with this kind of scenario over the course of the series. An obvious character arc is apparent if one watches the Mountain Villa Bandage Man Murder Case, the Moonlight Sonata Murder Case, the Distinguished Family's Consecutive Accidental Death case, the Dissonance of the Stradivarius Murder Case, and the Detectives' Nocturne in chronological order.
You can make the case that he starts out as a selfish Jerkass, but as the series progresses and Character Development sets in, becomes more attuned to the human nature of the cases, especially after the Moonlight Sonata case since in Episode 78 when Miyuki Hyuuga tries to kill herself and Conan thwarts it, Heiji explicitly asks why he did that, and Conan says "a detective that allows a suspect to commit suicide is no better than a murderer", Moonlight Sonata flashback included.Some put him somewhere between Intelligence Equals Isolation and Insufferable Genius.Genius or selfish, immature Jerkass who places himself above the others and doesn't really get the meaning of death and for whom each dead person is nothing but challenge?.
(It also helps that he tends to be more street-smart while Conan is more book-smart - Kogoro has more insight into peoples' emotions) Chapters 853-55 reveal that Kogoro believes his "sleeping Kogoro deductions" to just be his true, brilliant self coming to light, with the drowsiness and sleeping a consequence of all his brain cells working at full power. There have been several other times where he actually got it mostly right, and several times where he solved the case and only needed a couple hints from Conan, or in one occasion, not only solved it but got a couple details that Conan missed. Whenever Ran or Conan are threatened, he actually becomes scarily competent (Kinda like Inspector Gadget whenever he knows Penny & Brain are threatened). Kogoro already isn't a bad detective he's just got an extreme case of Tunnel Vision and wants things to be done as fast as possible, so he'll come to one conclusion a detective would, but then insist he's right until proven wrong.
Appropriately, when she and Gentleman Inspector Shiratori get together, her adorkable levels start rubbing off on him. Conan's teacher Sumiko Kobayashi is not only really pretty, but a very sweet Nice Girl who often goes adorkable when she fangirls over her beloved mystery authors and the Japanese Police (she wanted to be a police woman before choosing to become a teacher), or when she tries to become the Detective Kids's "manager".