The majority of great MSDOS games run in 640x480. Most of the games that didnt were 3d games like DOOM. Although you can find some REALLY OLD MSDOS games like Bards Tale, etc... that run in 320x240, but not many good games ran at that resolution. C&C RA is 640x480. Most games used 320x240 only when that was the "standard" resolution with 4 to 16 colors. Once VGA became available, everyone jumped on it and never looked back. 3d games ran a bit slow at higher resolutions like that, so they all supported the lower resolutions like 320x240 (and as GPDoom shows work great at that resolution)