Not sure what your monitor setup is, but a CRT with scanlines makes things look much sharper. Modern LCDs blur everything not at their native resolutions.
CRTs have both round phosphor dots not big square pixel cells (making graphics twice as blocky even at native resolutions) but lack of scanlines on LCD also makes images twice as blocky as CRT.
Load a 640x512 pixel 256 colour picture on an Amiga with an RGB monitor cable on say a Phillips/1084S and then go and view that same image on a laptop with a resolution of 1280x1024 native LCD in 200% (so the pixels map perfectly and there is no hardware smoothing due to resolution mismatch of using different windows desktop rez to 1280x1024). The image you see on the screen of the Amiga looks higher resolution.
But yes most PAL games <> 320x256 and stuck with stupid 320x200+huge border so they didn't even use the full potential graphics quality Jay Miner and co designed for them! *face palm*
(not saying this is the reason btw)
