Almost all headphones/earbuds/IEM's will sound better than the ones provided by Apple. If you go to a good store you can listen to a bunch and pick the one you like best, alternatively, buy a pair from a box store and return them if you don't like them.
If you want people to give you actual suggestions, we need your budget and type of headphones that you want (over the ear, on the ear, earbuds, in ear monitors, etc.), type of music you listen to can also be helpful.
If you want to research yourself, browse around headfi.org
Good luck.