I didn't like the HE500 for gaming until I did the grill mod. Now they are excellent. I'm surprised how much of a difference it made.
Previously I used the Q701's to game with (which are excellent for gaming). The soundstage of the modded HE500 still isn't as good as the Q701's but it is getting close enough that I don't really care so much anymore. The additional weight and bass of the HE500 plus the soundstage (modded) makes it a pretty decent gaming headphone to be honest.
If you are looking at competitive, then the AKG's will have it beat. Fun, HE500.