Eh, his short stories were where he shined (heh). Read: Shawshank Redemption / Green Mile.
Actually at the end of some of his novels, he'll sometimes have some short stories that are usually better than the rest of the book. Sort of a reward for sifting through the rest of the text.
Thing is, it is indicative of his writing 'pedigree' if you will. Being his influence was driven from Poe and Lovecraft, it is perhaps because of this that King is perhaps good at short stories, not as effective as a novelist. Whilst the aforementioned Poe and Lovecraft were 'masters' of the craft, their efforts were more limited to short stories, as this allowed for building of suspense and then a quick gruesome resolution.
Perhaps where King differs though is in the Characterization, hence allowing him to draw a short story over 300 pages. I suppose you can love or hate him. Or, be indifferent. I have consumed quite a bit of his work, I have to admit I didn't mind them when I first got into them. After a while though, they got rather samey, but then I guess the same could be true of Lovecraft/Poe. But at least with the latter you know you won't be spending a week or so on the one story.