I'm not sure about the Japanese cartridges but 4 of the easiest ways are the color, the label, the back, and the contacts.
it's a little hard to tell but the color of the one on the left is a little lighter shade of gray and you might see fonts are off on the label (gameboy advance logo for this one)
the font on the back of the cartridge will tend to be larger and not as bold
finally the nintendo logo should appear like this above the contacts
Not like this
Hope this helps