Sometimes, when I quit Battlefield 1942, the screen resolution goes to a horrible 800x600 which makes everything, well, horrible. I used to reboot to fix it, but then I found a solution that's much nicer, plus it's also handy if you like to play with screen resolutions too!
If your screen resolution is, say, 1920x1200 then to reset it back use this command:
xrandr -s 1920x1200
Replace those values with your screen resolution and you're good to go!
Maybe add this to a script as a shortcut, or as a keyboard shortcut.