I love mysteries.
That is to say, I love a good mystery.
There are also different degrees of goodness in a mystery. Example, there’s a difference between The Hardy Boys and Agatha Christie. Both are good, but dear old Agatha has a little more oomph to her writing then is generally found in Hardy Boys. (Not to insult the Hardy brothers, they are my favorite pair of boy detectives, except maybe Harry Potter and Ron Weasley.)
I think the thing that unites all good mysteries, however, is are characters with some moxy. Polktitude, that’s what a successful solver-of-mysteries needs. Even if Sir Aurthur Conan Doyle’s crimes were still brilliant, who would have cared about them without Sherlock Holmes? Can you imagine if Watson was the main character? The Adventures of John Watson. Eww. No, Sherlock gives the series it’s edge. It would be boring without a rude, drug-addict, conceited loaf for a hero. But we love Sherlock, no matter his quirks, because of his brilliance.
Not that straight heroes can’t be interesting! No one could fault Hercule Poirot’s moral integrity, but he’s still not boring! All of the truly great mystery heroes are quirky in some way!