Moriarty *on his own* doesn't annoy me a quarter as much as Moriarty in a Holmes story. It's perfectly fair game, IMO, to take a canonical character and explore their life outside their storyline - Carole Nelson Douglas got a lot of life out of Irene Adler.

But when it's Moriarty and Holmes facing off... well, if I want to watch a pissing contest, I'll watch Lethal Weapon or something. Not a detective show. (I've gotten to the point in the Great Detectives audios that I stop listening the moment someone says the M name.)