Headphones really come down to how much money you are willing to spend (you can spend a lot). That said, unless you're a real audiophile, after ~$100...the gain/improvement per dollar really plummets, imo, and so I always suggest that as the pricepoint for non-audiophile friends looking for something better than their Walmart Sony/Koss/Bose/Pioneer headphones (or, even worse, the headphones/earbuds that came with their MP3 player/phone).
If you are an audiophile, I don't think you really need recommendations.
So, for the ~$100 range, I'd recommend a pair of Sennheisers. You can't really go wrong with their lower-end side of their HD line, and ~$100 generally offers a marked improvement over $10-$50 department store brands. Their HD 448 can be found for ~$80-$90. Sennheiser is an established name in the headphone business. You can go even cheaper with their HD 428 @ $50, while still being an upgrade over cheapo headphones. (Disclaimer: I own a pair of HD 595s as my "comfort" headphones-ie: marathoning an anime TV series-due to their loose, open design and a pair of HD 600s...that despite being the better sounding headphones, doesn't get used as much due to the closed, tighter design-but have tried both the 448 and 428s).
I would strongly suggest staying away from "gaming" headsets, as most of them are low quality with a huge mark-ups stemming from slapping the "gaming" marketing label on their boxes. ie: While many are in the $100-150 range, their sound quality really puts them in the $50 range. There are probably exceptions, and one of the things you should be on the look-out for if you do intend on a gaming headset is to avoid those that use USB. Two 3.5 mm jacks (one for the headphone, one for the mic) usually means the manufacturer is serious about the sound quality.
If you want a good set of earbuds, be prepared to pay a bit more for the same quality as a pair of headphones, or pay the same for inferior quality. I use the $99 Shure SE215s for jogging, or when I am flying/on a train, but when at home, I'll always use around the ear headphones instead.
Anyways, headphones are like shoes. Not really worth paying for cheapo generics, nor worth paying for those Air Jordans (ie: flashy mass-market gaming headsets). Spend a little bit of money to get something with some quality behind it, and think of it as an investment that will provide enjoyment/comfort for years.
And, like anything, this is just my opinion.