Some closed-back, over-ear headphones I've picked up that people recommend for gaming:
- AKG K550
- Audio Technica ATH-A1000Z
- Audio Technica ATH-MSR7
- Beyerdynamic Custom One Pro Plus
- Beyerdynamic DT770
- Shure SRH940
- V-MODA Crossfade M-100
You should probably shy away from bass-heavy headphones when it comes to competitive FPS gaming. Look specifically for a wide and deep soundstage, imaging, (instrument) separation and detail retrieval.
Soundstage is perceived space and environment of sound. It determines whether the sound is perceived to be coming from inside your head or beyond the drivers and around you. It can be compared to virtual surround sound; both attempt to produce the same spacious, three-dimensional effect. VSS can sound more ambient and immersive, which will depend on the processor (CMSS-3D, Dolby, SBX, etc.) The reason why stereo should be considered over VSS is that VSS degrades the sound quality and diminishes detailing due to compression from digital processing. You might also experience less accurate imaging and separation. Imaging determines how accurately sounds/objects are positioned. Imaging is inherent to the audio content, so if the game is recorded or mixed poorly, a headphone with good imaging won’t improve the original source. Separation is separating individual sounds from a range of sounds. Good separation properties should make it easy to filter out or discern overlapping sounds from other sounds and track them.