Following 100 Great Short Short Science Fiction Stories, this should really have been entitled Another Hundred Great &co: the majority of the stories collected here -- by authors from Asimov himself to Zelazny (a master of the very short genre story) -- seem more easily categorised as SF or horror than as fantasy. I did start tabulating themes (pacts with the Devil or his minions; 'three wishes'; ghosts; vampires, werewolves and that ilk; alt history ...) but was distracted by some of the puns I encountered herein. Even without quantitative data, though, I'd maintain that the majority of these stories aren't strictly 'fantasy' in the contemporary sense. And I'd also like to point out that presenting the stories in alphabetical order by title means that similar tales may be clumped together, to their detriment. When it comes to an anthology, contrast is good.('The Third Wish' followed by 'Those Three Wishes'; 'Deal with the D. E. V. I. L.' by 'The Devil finds Work'.)
The stories collected here were published between 1940 ('The Haters' by Donald Wollheim) and 1984 (several stories including 'Vernon's Dragon' by John Gregory Bettancourt: this anthology's copyright date is 1984). It's a whirlwind tour of the (primarily) American short-fiction market over that period, from the ancient horrors of Lovecraft to the psychological nasties of the sixties to the smaller apocalypses and stranger worlds of the eighties.
It is perfectly possibly to write a neat, well-formed story in a thousand words or less, and many of these authors manage it. James Gunn's 'Feeding Time' will stick in my head (and is proof that there's room, even in a story this short, for pacing and suspense). I'd read Wollheim's 'Rag Thing' long ago, not remembering title or author: the story's stood the test of time. There are clever stories, wry stories, stories that are deeply surreal (Raylyn Moore's 'Getting Back to Before It Began', about a bus ride to the end of everything, to where there are no names for places ...) and stories with the simplicity of a fairytale (Jane Yolen's 'The Lady and the Merman' is a bittersweet delight, wonderfully visual and melancholy).
There are also quite a few stories that exist to support a pun or a one-liner (not my thing, but fine in moderation), or to explore a hitherto-murky aspect of a classic story -- literary fanfiction, if you like, where a crewman from the Flying Dutchman makes his escape and is rescued by the Marie Celeste; where the ghosts from Hamlet plot together to ruin everyone else's stories; where God welcomes Adam and Eve's rebellion. One thing that does strike me about these stories is the sense of fun -- that these are tales their authors produced for the hell of it, because they wanted to, because the idea suddenly popped fully-formed into the writer's head.
A good anthology to dip into, but be prepared to groan at some of the really dreadful puns.