Based on my own experience of using ipods and iphones over the years, the stock earphones that Apple include with their products have always sounded thin and cheap compared to 3rd-party earphones. A cheap $10 pair of Sony earphones I bought even sounded a whole lot better than the stock pair.
About your iphone's earphones breaking down after a mere month, happened to my old ipods and my iphone's stock earphones as well. The ipod stock earphones I had lasted a around 2 months. The iphone stock earphone only took 1 month of seldom use for it to start to cracking. After a few days, the left stopped working completely. Never used the stock ones since.
But, of course, you or other users' mileage may vary.
