Let me preface this by saying that I'm definitely an anal gamer, especially when it comes to graphics.
Does anyone have the Asus VG248QE w/ G-Sync installed? How did you set up your color calibration?
I found a good .icm that brings gamma in line, but that only affects DWM on Windows (i.e. Windows Desktop). Fullscreen games still have fucked gamma even after playing with the in-game slider (sidenote: World of Warcraft actually has a setting to grab gamma from the desktop, in fullscreen mode, so that's cool). Using a custom .icm + softMSCC (to set sRGB on the monitor and adjust brightness and contrast) + fullscreen windowed is the only way I've been able to get games to look okay, but fullscreen windowed disables G-Sync, so fuck that.
Is there someone out there as anal as I am about color calibration? Please let there be someone who has solved this issue. Search engines have failed me.