i am not sure if you can use 28 or 75 for landscapes!!..it will be too narrow field of vision. although 18 could be acceptable but yet not sure abt the quality of 18-200 at 18mm. Although from my exp all the lenses except a very few PRO grade ones can give decent to very good images depending on your style. Few tips
- Aperture f8/f11
- Lowest ISO possible.
- Use Tripod if shutter exceeds 1/30.
- Remote trigger to avoid vibrations.
- Experiment with hyperfocusing for landscapes
Another advice could be to use lenses that have VR (in Nikon term)
If still you are not satisifed then you can try other lenses as mentioned in the thread earlier. Myself i am using 16-85 and the results are very good.
DeepS
It might not be as common, but longer lenses definitely can be used for landscapes.