The newer nvidia drivers are pulling colour profiles, gamma, brightness, etc... from the OS (your desktop settings) and overriding some game and application settings.
Especially those using older game engines, using older directx, glide, opengl, older shader models etc....
Skipped frames, messed up draw distances, hard lights and shadows.
(newer games look great, though...)
You may notice a difference if you switch any affected game between windowed mode and fullscreen mode (alt+enter or menu)..
If there is a some difference between the gamma, brightness and colour between windowed (application profile) and fullscreen (desktop profile) then one workaround is to run in windowed mode and simply strip the border.(metacity / fluxbox --replace), but since you are using ubuntu this will strip all borders from all windows...
The other option is to force the settings for the whole machine, using the nvidia software, to ensure the colour range - more important, the colour profile (ICC) - is correct [for your monitor] and is set to full.
Also calibrate monitor, probably have to use gnome colour manager (gnome-settings-daemon) / xiccd also.
Many older games have had this issue lately (not ones from the 90's, however...) - if you were using windows, it would be easier to fix. Windowed mode and border-stripper does the trick.
You might try to roll back to driver 188.8.131.5213 (388.13, not 388.31 or whatever it is now).
Or force the game to change its brightness and gamma settings by editing the config files (set to read-only to prevent over-write).
Don't forget there is likely a brightness function for your display for fine tuning.
Unfortunately - games from the dx9ish era are starting to show many issues with graphics, physics and scripting as more and more Call of Duty / Assassin's Creed / Tom Clancy's: Shovelware is released and OS and hardware drivers focus on superficialities such as FPS and realistic, open-world. free-roam, VR, cinematic boob-bounce physx more than supporting enjoyable game-play - because that's what gaming is now: Tits bouncing at 4k, 120FPS, displayed on a TV (that likely max's 30FPS).
I believe the TDM team have recently discovered why some games are capped at 30-32/60FPS for physics sake, while trying to squeeze more FPS out of a 59.94hz display on a laptop with an intel on-board graphics card...
Incidentally - The Hobbit was filmed at 48FPS and some people complained it was too lifelike and broke their suspension of disbelief:
Most movies are 30FPS.
Anyway - try setting the brightness and gamma using the config files in the TDM directory - trial and error ought to do it. The GUI isn't playing nice with the nvidia drivers.