What makes a good arcade conversion versus a bad one.
Translate the essence of the game.
Find a visual style that works well within the constraints of the system.
Utilise the sound hardware in interesting ways.
Essentially it's all about exploiting the hardware as opposed to being "Arcade perfect" because that's when you fall short, when you're trying to duplicate the visuals, to the point where in a screenshot it looks at least similar or close to the arcade game that often results in a choppier, less playable game that can’t support, the visuals don’t support the game well in those conversions.