I would suggest you only original headsets of Apple, such as MB770GA or a more expensive but better MA850GA.
Of the not original earphones I would buy iCandy. But... Some people are also very satisfied with compatible accessoires. They can be good if you don't have such great demands. But for good qualiti sound I would buy a little bit more expensive original piece, which would last longer en deliver incomparable sound quality.
My brother has a set of JVC Marshmallow ear buds for his iPod, they're amazing. Great sound quality and the bass is insane, for what they are. They work very well, no distortion. IF I used my phone for music those would be the headphones I would get.