That's a hard question to answer. I tweak my config file extremely on CSGO to give me the upper hand over users on stock settings. Some forget to swap to the headphones DSP from speakers, which really makes things sound off. Some other folks use virtual surround and other DSP like Dolby Atmos Headphones or whatever it's called on Overwatch. All DSP does is add latency and makes everything worse to a purist like myself. Keep it all on stereo…
There are probably a few hundred CSGO tutorials, map breakdowns, strategies, and so on that can help teach you the game, settings to tweak, individual sounds, maps, positioning, etc. Once you know the game, it's apparent as night and day if a headphone is excelling or falling short in one aspect or another. The S-logic tech for Ultrasone headphones works for my ears. However, when you get shot in the head while wearing a signature pro — I'd jump out of my chair and shove my keyboard forward from flinching so hard. The peak for whatever frequency that was would be so piercing and loud from dead silence that I deemed it unplayable after a while.
Maps like Nuke on CSGO have sounds specific to only it — down to certain parts of it. You can hear if someone is in a vent, 2 stories below you from across the map if you're aware of the game and maps. The T1.1 and HD800 can hear from spawn to spawn on dust 2. Talk about an unfair advantage over the competition. It's just like having a 144 Hz (or higher) display vs. a very quick 60 Hz monitor vs. a slow TV, with interpolation/upscaling, running through an AVR, and anything else in the chain that adds latency of any sort (display lag, audio lag, input lag).
Battlefield 1 has excellent audio as well with a lot of potential for XYZ cues since the maps are huge. Many are on slopes, have trenches, bunkers, buildings, and so on. There are planes, mortars, bullet drop, etc. You can hear where the enemy/allied fire is coming from.
Footsteps really stick out in a good pair of headphones. Something like the TH900 can have too much bass — explosions and gunfire drown out footsteps which can hurt your ability yo know where enemies are located, moving, and where you need to move to get into a position that has advantage, stay where you are, or proceed to flank appropriately. That sentence was too long.
Rainbow Six Siege has a lot of vertical aspects to the maps. You'll be breaching through walls and such. Footsteps are very important. If you know where someone is on the other side of the wall, ceiling, or floor without seeing them, it's game over for them.
Overwatch has a lot of vertical maps too, but their sound design, engineers, and/or game engine is poorly designed. It's the worst game I've played for audio in a while. Even so, the T1.1 is like having pocket aces up your sleeve. The HE500 is almost as bad as the HE400 on OW. The Eikon isn't very good either. I'm going to blame the game and not the headphones since it's isolated to just it (OW).
DOTA2, HotS, LoL, Diablo III, StarCraft II, etc. aren't the right genre to test these aspects. Any headphone or headset will suffice for something like that. Third person shooters aren't as picky as first person shooters. Racing games, RPG's, and MMO's aren't really picky either.
From the way I've heard the image of the LCD-X, Elear, and Utopia described, I suspect that they would suck for online competitive shooters entirely. Too in your head with a pea sized image. Not a problem for music, but definitely a problem for higher tier competitive gaming.
Note: I likely take this subject more seriously than 99.99% of the population. I've been on amateur teams when I was younger and have won prize money before. That competitive nature doesn't just leave you. I've even bested the #1 player (at the time) in the world in Overwatch. Not that it does me any good in the real world. Lol. I've been SMFC (never hit GE) on CSGO playing casually with friends who were essentially being carried up to those ranks. Even Rocket League, I've bested some pro players in the upper echelon of ranks with my sibling and our mutual bud(s). Tryharding is in my blood.
Edit: I find FPS titles to be very effective in testing soundstage, imaging, and separation between headphones, dacs, and amps due to the game treating all hardware equally. What I mean by that is everyone is having the same experience if they're set to 2CH stereo and using the headphones preset. For music, only those involved in the process know what the original recording, mixing, and/or mastering sounded like when producing the original album/tracks. Anyone/everyone can evaluate game audio. Movies being made for surround sound… downsampling to 2CH isn't quite the same. If you have Windows set to 8CH and the game set to 2CH, umm… whoops. XB1 or PS4 set to 7.1 on their AVR and plugging a headphone into the hp jack and/or setting it to stereo mix is still going to impact the perceived image. It becomes too altered and wonky imo/ime. If you're going to use surround sound, stick to surround; if you're going to use 2CH stereo, stick to 2CH stereo. Avoid mixing channels up or down if/when possible.
Another Edit: I have a proper 8CH (7.1) setup for console use. A literal 7.1 speaker system is still better for positioning than a perfect 2CH headphone system. Both options are better than virtual surround. The T1.1 is the best pair of headphones you can own for FPS due to it's circular, holographic image that's not too much of any one axis (X, Y, or Z). An HD800, AKG __ aren't perfect circles in a sometimes problematic way.
The last thing I'd add, a bass neutral/lite headphone is going to be easier to work with on following positional cues in games. Some v-shape headphones make the vocal range too quiet compared to the rest of the FR. If/when you're using in-game or third party comms/VoiP, this becomes a problem almost immediately. Either turn down the game or increase the gain of VoiP. When trying to remain bitperfect, it's the little things that'll get you. I can have Windows, my game, and VoiP at 100% volume across the board with an LCD-4, Ether Open, HE-500, and T1.1. Many (almost all) other headphones cannot follow suit. I don't just play by myself, so that's quite a large factor in my grading/ranking list.
Last edit: Oh — my apologies for the off-topic discussion as well. Some of it can be cross referenced with Levap's breakdown of how he prefers to listen to metal on a genre-to-genre basis. Some genres can sound too thin, while others are maybe too congested depending on the individual's preferences. Too cool or warm in tonality as well. This is why there's no perfect pair of headphones for every use or even individual. If one person loves prog and the other black, well — that's a conflict of interest to an extent. Lol. If someone is playing an MMO, MOBA, RTS, or racing game and simply wants to listen to music and doesn't even use in-game audio, that's completely different as well. Really there's a lot to mix-n-match. I don't play games and listen to music simultaneously anymore. I like to focus on one thing at a time, giving it my full attention that it rightfully deserves. I don't even listen to music when I'm driving — don't want to be distracted.
