Most Arcade cabinets have inclined monitors. The reason for this is ergonomics: it's more confortable, specially with upright cabinets. With sitdown cabinets, I don't consider much angle is necessary, specially with large screens. In fact I've noticed that japanese sitdown cabinets force the users to a posture that is not very natural, too straight, coming close to the excessively inclined screen. Do you think that the inclination of monitors in cabinets has also to do with avoiding straight radiation to the player? If you notice, although the player can see the screen, his head is not on the way of the screen radiation, supposing that it's parallel to the screen. I don't know if I've explained this well, so, if it's not clear I can add some pictures.