Hmmm, I think the fact that the connection of monitor to graphics card has remained the same for all this time has helped confuse the issue a bit.
VGA as an official graphics standard resolution calls for support for resolution up to 640x480 and 16 colours originally. This of course has been extended to support 256, 65,000+, etc colours.
Technically 800x600 is the SVGA standard and higher ones are called XGA, SXGA, etc.
However they all use the same connector. So to answer your specific problem, the monitor should be able to plug into a standard VGA graphics card and support a minimum resolution of 640x480.