... and most arcade games are jaggy by nature. The games are coded at a fairly low res, at least compared to todays games, so the jaggies abound. Hell, "jaggies" wasn't even really a term back in the heyday of the arcades, since they're was nothing to compare them to.
Playing Mame games on a PC monitor as well will further make the jaggies stand out since the monitor is far sharper than an arcade monitor.