One would think mine must be Hercule Poirot and one would be right.
I like thinking about “the little grey cells” solving a puzzle, because I’m an armchair kind of solver. I like to imagine I could also match wits with the villain rather than fists.
Sherlock Holmes, of course.
Nero Wolfe, of course.
Currenly, I. M. Fletcher. I found a bunch of the Fletch books at a used bookstore and am currently enjoying them, very much. 
Actually, I love Hercule Poirot and Holmes.
I must say that Monsieur Hercule Poirot is the best fictional detective. I absolutely love what Agatha Christie did with her invention. I also love his bumbling sidekick/friend, Ariadne Oliver. I can see her now, her pieces of false hair falling off and Poirot, in his gentlemanly way, giving them back to her. She cracks me up. I don’t care much for Miss Marple or Tommy and Tuppence. They just get in the way of a good story; but, of course, that is just my opinion.
Have you read “Evil Under the Sun” by Christie? It is the most delicious book I have ever read! The only book I like without any real detecting is “And Then There Were None”. Chilling!
The premise is of course * fictional * detective, so Holmes is out…
<grin>
How about Gideon Fell?
Lord Peter Wimsey
I second that.
Sherlock Holmes is at the top of my list, and I’m beginning to like Nero Wolfe, but the one I’d like to plac near the top of the list is Djen Djieh Dee, a real-life Judge from 5th century China, hero of a 17th century Chinese biography, and of a series of novels by Dutch author H. Van Gulik (and of a less well-known book, Deception, whose author I cannot recall). Nicholas Meyer, the unsung master of the TV movie, turned van Gulik’s ** Judge Dee and the Haunted Monastery** into a wonderful TV movie for ABC back in the late 60s/early 70s. Each of van Gulik’s books conists of a set of interlaced mysteries, and are well worth seeking out.
C. Auguste Dupin. Although I’m pretty sure Mike Hammer could kick his ass in a fight.
One more for Nero Wolfe.
I know a guy whose given name is Mike Hammer. He’s somewhat less cool than the Spilane character.
My age is showing----SAM SPADE on the RADIO----HOWARD DUFF.
“Oh Sam!”
“Oh Effie!”
Dirk Gently
Philip Marlowe.
I’d put Sherlock Holmes in the top spot and let Peter Wimsey and Father Brown fight it out for #2.
Inspector Morose. Sorry, Morse.
No-one else could solve so many crimes and still look so miserable about it all. Alright, perhaps Dana ‘po-faced’ Scully off the X-Files.
Best TV detective Hercule Poirot, played by David Suchet. But I think that Lord Peter Wimsey is the best, even over Hercule.
In light of the fact that I happen to think that The Maltese Falcon is the best damn movie ever made I’ll have to say Sam Spade, formerly of Spade and Archer, but that was before Ms. Wonderley camen into the office looking a helluva lot like Mary Astor and Miles fell hard for her. Well, it turns out that…oh, go watch the movie.
You’ll also be kind enough to notice my sig line.
Best girl detective: Kinsey Millhone
Best really fat detective: Nero Wolfe
Best tough guy inna hat detective: Philip Marlowe
Best T.V. detective with a glass eye: Columbo
Best weird fantasy series with a dead guy for a partner detective: Garrett (by Glenn Cook. Everyone knows the rest)