While pixel density is good, there is no substitute for pixel size ie, larger sensors. Hence the full-frame 35mm and larger sensors will always produce better images. I have a Sony RX100 and its images are superb for a pocket camera -- a combination of the 1 inch sensor and fine Weiss glass.
I studied photography before digital and the same was true then: larger formats equalled higher quality particularly for landscape and scenes with specular reflections. The reason was explained to me like this: there is a tree with shiny leaves and these leaves have specular reflections (reflecting the sun directly) so there are extremely small but very bright points of light. These specular reflections hit the film/sensor and spread around a bit. If the grains/pixels are small the highlights will spill into adjacent grains/pixels and reduce sharpness.
I studied photography before digital and the same was true then: larger formats equalled higher quality particularly for landscape and scenes with specular reflections. The reason was explained to me like this: there is a tree with shiny leaves and these leaves have specular reflections (reflecting the sun directly) so there are extremely small but very bright points of light. These specular reflections hit the film/sensor and spread around a bit. If the grains/pixels are small the highlights will spill into adjacent grains/pixels and reduce sharpness.