Boris, you have gotten good advice about lenses and technique.
If you are concerned, shoot for a while with only your best lenses and see if the images improve.
But the comparison you have done with another photographer's work is not meaningful. Is he a better photographer than you? It sounds like you regard him as such. Firstly become the photographer he is (using your best lenses), then repeat the comparison.
You mentioned a concern about representation of light and dark areas in your images. Are you using a D or DS? If so, high contrast situations will always be a problem for you. Like me, you live in a sunny place where there are always strong contrasts between light and dark. (I live in New Mexico.) If you shoot in the mid-day hours (as I often have to), you will always have problems with contrast and washed-out colors.
The solutions? Shoot earlier or later in the day. Be careful when composing and/or determining exposure to avoid blown-out highlights or black shadows. Shoot in RAW. Learn more about post-processing.
If you are shooting digital, you might want to save up for the DA 16-45. At f8 it is the equal of some very good primes (including the new DA 40 f2.8 Limited), and will give you a good range of focal lengths.
These were both taken with the inexpensive (and a bit soft) F 35-80 f4-5.6. My travel health doctor and nurse liked the first one so much that they borrowed the negative and had 30 x 40 inch enlargements made (that's just shy of a meter on the long side). You do not need to be limited by lenses.
http://pug.komkon.org/00octo/Djenne_Market_Day.html
http://pug.komkon.org/01jan/Woman_2_Nampala_PUG.html
Joe
