Basics to consider in headphones
Thresh's comments in BLACK
Kenn's comments in BLUE
They keep my ears warm
I think the most important things to realize are the practical aspects as well. We're not high-end stereophiles, and personally, my primary reason for buying headphones isn't for music - it's for games. Unfortunately what this meant is that I couldn't really test the quality of the sound at the store - I had to buy it, bring it home, and plug it into my computer before I could be sure I was happy with it. Before I bought them, however, I did look for a few specific things.
Price: Since I was going to be using my headphones quite often, I was willing to make them a worthwhile investment. For me, that meant spending a little extra for better sound and added comfort wasn't a big deal. When I first purchased these headphones a little over a year ago, the total cost came out to around $200 or so. Now, you can easily find the V600s for under $100 - still a bit high-end for most people, but not quite as painful a hit as before.
Comfort: If you play as many games as I do, prolonged use is going to be a big issue - some smaller headphones press directly against your ears, and after an hour or so, you'll definitely notice it. The V600s completely encompass your ears, fully removing the pressure from them. For me, this has a double-benefit because I can make out sounds coming from the left/right sides more easily with the drivers farther from my head.
Sound Quality: In competitive 3D games such as Quake and Quake II, being able to discern where your opponent is by the sounds he makes is critically important. For this reason, it's important to have a set of headphones that can reproduce the entire sound spectrum clearly. The Sony's do this very well - there are never any crackling or poorly rendered sounds. Also, some sounds are very hard to hear, even with a good speaker system. Get a decent pair of headphones, however, and they become very clear. Have you noticed the soft background hum when you use the railgun in Quake II? Well, it's hard enough to hear when you use it, but with a good pair of headphones, you can actually hear when you're opponent is using it as well. It's the little things like that can make a big difference.