As we all know, when these games were originally released 20 or more years ago there were no wide screen monitors, only monitors with the regular square aspect ratio.

So i was just wondering if there's any distortion in the presentation when playing these games through GOG on widescreen monitors?

There's distortion in that they're stretched to fit the screen if you want to run fullscreen. Doesn't make anything illegible though.

There's the possibility to tell DOSBOX if the aspect ratio should be corrected or not.
You can also enhance graphics with some scaler options like HQ2X.
See DOSBOX wiki for more details:
http://www.dosbox.com/wiki/Dosbox.conf#aspect_.3D_true_.7C_false