In the 'computer world' CGA and EGA are digital video specs with 4-bit color color depth (16 colors max).
In arcade machines, these specs are analog, so the number of colors is determined by the board.
Now that we have the difference out of the way...
CGA refers to a monitor that can handle a 15.75 khz scan rate (~15,750 lines drawn per second minus a few for the beam to return to the top corner of the screen). This gives 200 to 250 lines of resolution at 60 FPS. Also called Standard resolution.
EGA refers to a monitor that can handle a 24.8khz scan rate (~24,800 lines per second). This gives about 384 to 400 lines of resolution. Also called Medium resolution.
VGA monitors can hande 31.5 khz (31,500 lines per second), giving 480 to 512 lines of resolution.
Capcom vs SNK has a CGA monitor I believe.