it's not ideal, but romlister can help with some of that.
I assume your monitor can do 640x480, so you're looking for all games at or below that resolution?
here's how I did it with my arcade monitor machine:
generate a full list of all roms (or make a list based off your available controls) and then output the list as a CSV and include the video width and height in your output. bring the list into a spreadsheet and sort it on width and height and you can chop off the list when the resolution gets higher than your native.
doing this was kind of cool, as I found (I have a vertical cocktail machine) that some horizontal games from the early days were still less than 480, so they played just fine vertically in their native size.