ZDoom

One possible reason based on the screenshot sizes. The ZDoom full screen image is 2560 x 1440 pixels, the cropped GZDoom 3103 x 2879. GZDoom by default uses the display's native resolution. ZDoom's 2560 x 1440 pixels might have been the maximum. So your screen in GZDoom is now double more sharp ...

EDIT: Sorry, this is a duplicate of a thread I already made earlier. I was having some issues with logging in and thought at first that it wasn't created. It lacked the screenshots and more details so here it is again. END OF EDIT So, after a long break, I came back to do some dooming. Last I used ...