Enter the Game (mode)
For many years, knowing gamers would be bothered by bad input lag, companies started adding a Game mode that would reduce input lag and allow your in-game performance to be tied closer to your personal skills and reflexes (for better or worse).
However, Game mode isn't magic, nor does it simply overclock the processors and jack up the performance. Instead, it starts taking things out. Color processing, noise reduction, advanced scaling, all of these aspects and more get thrown out or greatly reduced. As such, the image gets a lot worse. Scaling artifacts are much more likely. Color accuracy and even potentially color temperature tracking, all suffer. The image can get noisier as well. What specifically gets tossed varies per company, but the end result is the same: less input lag, worse image.
One of the most common offenders of bad input lag is high frame rate LCDs (120 and 240Hz ). The processing needed to fill these higher frame rates is intensive, and one of the first things to go in Game mode. However, ditching these higher frame rates means motion blur is greatly increased, so everything that moves, or if your avatar looks around, the image blurs. This can be almost as bad as the input lag in as much as it prevents you from accurately seeing your enemies.
Lastly, Game mode is not a guarantee of no input lag, just a hope for less. One TV I reviewed this year had seriously bad input lag, and while Game mode improved it, it was still significantly worse than other TVs.
(Quoted)