There are various grades of Nikkors. Some are less expensive
lenses for the mass market, others are more expensive for the
serious photographer. For example, I have a Nikkor 70-210
f/4-5.6 and a Nikkor 80-200 f/2.8. The former was about 1/3
the price of the latter, the latter a much better lens.
I have a Nikon Series E 70-210 that's even lower quality than the Nikkor 70-210 (such low quality that they wouldn't even call it a Nikkor, although it's serviceable for architectural photography and landscapes, which is why I've kept it for 30 years).
It's important to remember that Nikon sells kit lenses to go with the D3000, and high end lenses to go with the D3s, and lenses in between. If you compare the sharpness of a Nikkor kit zoom to a Cosina/Voigtlander 125mm macro lens, the third party lens will win all the time, but comparing the low end of Nikkor lenses to the high end of third party lenses says nothing about the quality of the companies.