>>24498314 (OP)Suggestion for a top ten (I probably overlooked someone major) —
1. Sherlock Holmes (Arthur Conan Doyle)
--- Power Gap ---
2. Philip Marlowe (Raymond Chandler)
3. Sam Spade (Dashiell Hammett)
4. Lord Peter Wimsey (Dorothy L. Sayers)
5. Hercule Poirot (Agatha Christie)
6. Miss Marple (Agatha Christie)
7. C. Auguste Dupin (Edgar Allan Poe)
8. Jules Maigret (Georges Simenon)
9. Father Brown (G. K. Chesterton)
10. Brother Cadfael (Ellis Peters)
This is definitely ranking the characters rather than the quality of the books. (The Maltese Falcon is a better novel than anything Chandler wrote, and Agatha Christie is overall the worst writer on the list.)
Dupin ought perhaps to be lower (he isn't really all that fleshed out) but the stories were so seminal I bumped him up a bit.
Some people really love Gideon Fell (Dickson Carr) but I could never take him seriously.