This review is from: Shadows Over Baker Street: New Tales of Terror! (Paperback)
The rule seems to be that if you can't write a decent, imaginative and convincing Holmes story, then write a "Holmes meets ..." story.
I've read recent stuff in which Holmes meets Freud, H G Wells (he meets him again in this collection), Dracula, the phantom of the opera, etc. etc. (If you want to see how tedious and grim this can be I recommend "The tangled skein" by D Stuart Davies)
Now he meets Cthulhu!
Oh Elder Gods!
To be fair, Neil Gaiman's "A Study in Emerald" is a gem. Witty, imaginative and showing a deep knowledge of the works of both Doyle and Lovecraft. Also "The Weeping Masks" by James Lowder I found honestly creepy and rather moving (Maybe helped by the fact that Holmes is not in it, so the narrator Watson is not forced to be the limited stereotype that most of these pastiches make him.)
The rest of the stories- well, don't set your sights too high, keep your tongue shoved into your cheek and accept it as the lightweight mish-mash it was bound to be. If you can manage that, then it's an enjoyable, if forgettable, few hours.