The issue might be lens/camera combo.
15MP on a APS-C is still pretty dense and the 18-200 isn't the sharpest knife in the drawer (of lens in the bag if you get my analogy). The denser the sensor the harder it is on lenses.
Are those crops at 100% or past 100%? Any image past 100% will look unsharp.
In general, I wouldn't worry too much how a photo looks super cropped. As long as it looks fine at the size you want to print (or display on your computer) then it is ok
Not sure I quite agree with the "unsharp" look - I had one image where it looked sharp at 200% too -> if you have some really fine contrast and differences occur over 1 line of pixels, then 200% will look quite OK too.