640×480 was also a big deal because, for the first time, the PC had a graphics mode with square pixels. Most computers at the time (except the Mac) had pixels taller than they were wide.
Fun fact: standard VGA can (just barely) do 800×600×4bpp. The VGA BIOS doesn't supply a predefined mode for it, so you have to do black magic similar to Mode X in order to use it. Pity Windows' VGA driver couldn't do that; it would've turned heads and raised eyebrows for sure!
@argv_minus_one
oh that's wild, didn't know it was possible to exceed 640x480 with standard VGA.
@stage7 @Wintermute_BBS