Tough choice. The Kate Bush LP reissues have been a huge success to my ears - Having said that I'm only up to the Red Shoes so far, so haven't heard them all yet.
Whatever you may think of The Beatles remastering, the reissue brings us the Esher Demos - at last freed from the sonic constraints of dodgy multi generational bootlegs - so that has to be up in the running.
The Buffalo Springfield What's That Sound? box set of vinyl reissues is superb, as are the latest Crosby, Stills & Nash vinyl reissues; CSN and Daylight Again, so all three are contenders.
However, my personal favourite reissue (and, now I've really considered the question, by a country mile, truth to tell), is the Don Rendell and Ian Carr Lansdowne Recordings box set from Jazzman. I have longed for this reissue for ages, and just when you think it'll never happen... Beautiful presentation, fabulous sound, and some of the finest Jazz ever caught on tape (and it's British!), this has to be the best vinyl reissue of 2018.