They don't matter.
What resolution your creations should be so that world's largest art museums want to hang them on their walls between the works of Michelangelo, Leonardo and Rembrandt? This guy got away with just one pixel.
Others take gigapixel images. And still trying to figure out what to do with them.
Go figure.
Moral of the story: don't worry about megapixels. Whatever you buy today, you get enough of them.
See also: