As a general statement, the greater the zoom range of a lens, the more of a compromise it is at just about every focal length. To be more specific, I have the original 18-200mm, which I bought before I became a lens snob. I hated way too many of my shots, in part because of vignetting at certain focal lengths and lighting situations and in part due to other issues. A superzoom is convenient, but your pictures will suffer.
So my answer would be the 18-55mm and the 55-200mm. Or spend a lot of money for the 24-70mm F/2.8 and 70-200mm F/2.8 and then get the 10-24mm DX for landscapes. Unless you're on a full frame sensor; then get the 16-35mm F/4 as your wide angle lens instead of the 10-24mm. (Mine is on order.)