is a 20.7 megapixel camera always better than 13 megapixel?

Is megapixel everything when it comes to a cellphone camera? I mean is it possible that a mobile has a lower megapixel but it can be higher quality for some other reason?

via Forums de téléphone cellulaire (en français) http://cellphoneforums.net/fr/general-cell-phone-forum/t365373-est-un-appareil-photo-20-7-m%C3%A9gapixels-toujours-mieux-que-13-m%C3%A9gapixels.html