Well I heard 3 causes of it
1. Bad posture
2. stress from it
3. and the radiation from it
I gave you an agree rating, but i only agree with the first one, the bad posture.
From what i understand you spend a lot of time on PC for your own pleasure, nobody forces you to do that, you do it as much as you want, and when you want to stop, you stop, so using a PC is a way (chosen by you and many others) to spend your free time could not cause stress.
Maybe you want to say "fatigue"?
That is completely something else. Being captivated by what you do on the PC you may not realise that you got tired, and you continue to do what you do past the time when you should take a break.
Bad posture, and it is impossible to have good posture while using a PC, on the other side, is a big, big factor when we talk about tinnitus.
I do not know much about video games. Do you use a head set while playing them? Cause in this case the head set can be the cause of your tinnitus, as you suspect. This is very possible. I played only a little video games and i know they are very captivating, and they "surprise" with unexpected, loud noises (explosions, etc). Those sounds are very unhealthy. The sudden increase in volume, plus the fact that those sound are "electronic", not like the natural sounds of everyday life, is not good for your ears
Our auditory system is not made for those kind of unnatural sounds, the same way our eyes are not made for the unnatural lights of the display. Those sounds made have damaged your ears the same way the radiation of the display is ruining people's vision.
If you cannot thing of another cause for of your tinnitus, then the sounds of the video games are the culprit. If something may have caused your tinnitus and if you do not like your tinnitus, i suppose, why do you persist in doing the same think that caused you suffering? Is like hitting with the hammer in the same spot! How do you hope to get healed continuing to do the same thing that caused you harm?
Once again, if you did not do anything else that can cause tinnitus, than playing those video games is the cause, a combination of bad posture and unhealthy, loud, sudden sounds.
If i were you, i would quit them for a long time to see what happens with your tinnitus.
There are a lot on things you can do with your PC besides video games.