In all the time I have been using an iPod, I've learned that the original ear buds that come with the iPod are my very favorite ear buds to use. Actually, they are my favorite head phones of any type to use. They just seem to fit perfectly on the outside of my ear canal and never fall out.
I do not like to use a head phone that demands that the earpiece goes right into your ear canal. To me, it is uncomfortable and I worry about hearing loss/damage.
I've been using other ear buds recently - until I won my new iPod, http://sharedreviews.com/r/48418-apple-ipod-8-gb-nano and now have the pair of ear buds that came with it. That is when I realized that they really are my absolute favorites. It seemed like a relief, after all this time, to be able to use them again.
The trouble with the Apple brand for me has been that they don't last. One side will always fail after a couple of months or so. I've always wrapped the generously long wire around my iPod to keep it from getting tangled when not in use. Maybe this hasn't been a good idea and is the reason they fail so quickly.
If you register your iPod with Apple, they will replace your first pair of headphones for no charge, which is great. I have found them online, though, for just $9 plus shipping which really isn't bad at all, and as I've now learned is completely worth the money for me.