UPDATE: After trying out my new Koss PortaPro headphones, I have found that they have something that my Telex headphones don't: bass.
These cost $30-40 instead of $10, but they are much better value. For cheap headphones for game playing, get the Telex phones; for music, get the PortaPros.
For instance, the Star Fox remix Barrel Roll's bass drum no longer goes "thup thup thup". It now actually sounds like a bass drum.