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There are different brands of smart phones available. Frequently two different big brand smart phones (Nokia, Samsung , Apple, Sony etc.) with the same Megapixel count have a different quality of image.
Whereas the DSLR cameras with same megapixel resolution have altogether best quality.
Why is it so?
There are a lot more to image quality than resolution (i.e. number of megapixel).
First of the light from the subject has to be gathered to the image sensor. This is done by one or several optical elements that together constitutes the lens. These elements can differ in quality and a low quality lens will not produce a high quality image no matter the megapixel count.
The next part to consider is the image sensor itself. They come in different sizes and technologies and this of course affects quality of the image too.
The software plays a big part in it too. Different manufacturers interpret the data gathered from the sensor in different ways and different adjustments are made in post to produce a final image. Some are likely bound to fit your taste better than others.
The reason smartphones can't compete with DSLRs is a combination of all of the above. Also the megapixel count tend to be very bloated in smartphones compared to DSLRs (even though manufacturers run a megapixel race here too). Megapixels are necessary and more of them is not worse but they are not the only determining factor to image quality.
Megapixels just tell you one thing: the number of individual tiny detectors on the sensor. They do not tell you anything about:
In short, megapixels are a very poor proxy for image quality. The important thing, though, is that this is true for all cameras, not just camera phones. It applies to DSLRs as well. The reason that you think that they're all better is that they tend to be better at all of the things above (starting with much larger sensors). And, because camera phones are at the marginal low end of many of the parameters (trying to squeeze everything in a tiny space at minimal cost) the differences can be amplified, while its true that any modern DSLR is generally at a decent baseline — there are differences if you look, but since they're all above the threshold of "quite good", it's less important to stress about.
Because the megapixel value is only one small factor in the process. The sensor size, sensor type, lens, exposure control, processor and software altogether set the quality of the image, not the number of dots in it.
However, you don't see "Digic V Processor" advertised too much as the buying public doesn't relate to it. They see "8" on this box and "12" on that one. 12 is better than 8.
People who do know the difference aren't influenced by big-letter marketing techniques. They also don't care too much about a phone's pixel count. Nothing with a lens/sensor combination that small is going to produce anything decent anyway.
