DxOMark tested lenses for the Sony NEX system
DxOMark are doing their measurements on unprocessed RAW files. They identified the best model in different categories.
According to DxOMark the SONY NEX Top Primes include Sony 50mm f/1.8, Sony Carl Zeiss Sonnar T* E 24mm F1.8 ZA, Sony SEL35F18 35mm f/1.8. Interesting enough the best prime DxOMark selected is the Sony 50mm f/1.8 costs less then 300 USD and the second best (Sony Carl Zeiss Sonnar T* E 24mm F1.8 ZA) is below 1000 USD. When it comes to Zoom Lenses my favorite one the Sony SEL1018 10-18mm scores highest.
One think to keep in mind is that while the SONY lenses score low compared to Canon L lenses we use. However the quality of the photos that you can get from a Canon L lense compared to the SONY lenses do not provide a different image, at least for me.