I gotta go with Everything's Eventual as his best short story/novella collections, followed by Different Seasons, Four Past Midnight, Skeleton Crew and Night Shift to round out the top 5. Gotta agree with If it Bleeds, too. I thought the Life of Chuck was some of the most self-centered fear-of-mortality crap he's ever written and shat into book form (Sorry,
@Dom Cruise!) and nothing else in that book jumps out at you the way the short stories in his other collections do.
As an example, "Blockade Billy" was probably the greatest novella in ages that he's put out, and sadly that will almost never become a big screen movie. Bazaar of Bad Dreams would be in the top 5 because of this story and for 'Ur' but unfortunately it also contains some of his most glurgy crap like "Mister Yummy" and a THIRD goddamn haunted car story in 'Mile 81'. (FOURTH if you count Trucks/Maximum Overdrive.)
And for DeathWatch 2022, I am calling Queen Elizabeth II. It's just been TOO goddamn long.