A close-up photo on most(not all) marquees with at least 5 mega-pixel capability would probably be adequate. You could also photograph it in 2 or 3 detailed parts. Obviously the better the camera, the better the results.
What I'm doing, with excellent results, is scanning all my marquees at 300 dpi in 3 parts. Scanning(and ultimately tracing) is the ideal method for artwork preservation.
You can upload your arcade artwork pics to the Library here:
http://localarcade.com/arcade_art/This is the main repository for arcade artwork at the moment.