I hadn't thought of the state of standards, but that's also true. However, mid-90's games that did do 640x480 generally did that in 256 colours, so they alread

I hadn't thought of the state of standards, but that's also true. However, mid-90's games that did do 640x480 generally did that in 256 colours, so they already had to deal with going above standard VGA one way or another. Very few games that I can think of used the VGA mode of 640x480 in 16 colours, and they certainly weren't first-person shooters.