Ive seen Ms Pacman on large sized monitors... and it actually detracts from the look.
Things are stretched out, more pixilated. And being too close to a larger monitor, makes it
difficult to see all of the action, without panning.
Now... If you are maintaining the original sizes, and using the extra display to make it good
to run either horizontal and vertical games on the same monitor... that could be a valid reason.
From my personal comfort, I found the 25" fighting game cabinet monitors, to be as big as
I could stand.
If its a pedestal cabinet... that puts the screen about 4 to 5 feet away... that thats a different story.
Those work decently for larger scale images.
With Pedestals, However., ..you do lose that close quarter magic, that comes from the typical
19" classic arcade cabinets. Those cabs with their black sides... act sort of like Blinders.. and
really make it much easier to focus, and be more immersed into the game. The sound also tends
to be better.. because its contained within that walled-in-space... so there is less outside noise distortions.
Another Exception to the rule.. could be the use of mounting it facing upwards, and using a half-silvered
mirror. This is used on games like Discs of Tron, Terminator 2, Lethal Enforcers, and a bunch of others.
The mirror bounce creates additional distance... so it looks and feels like the monitor is about 3 ft away..
and looks a bit Smaller. SO in this case... a larger sized monitor would help negate the screen seeming
smaller.. while also still making it further away from the players.
Additionally, one could install artwork behind the semi-translucent mirror, that could be backlit, to make
a 3D display. (like Asteroids Deluxe, Discs of Tron..etc)
There are some other reasons for a larger monitor... such as playing certain PC games that have small
text, more detailed images, and or higher resolutions. Graphics cards can do a pretty decent job in
scaling higher resolution video... to lower resolution displays. I believe some of them can / do, use
interlacing methods.
(actually, Tekken III has an Interlace mode that you can enable in the Service menu. Not sure if it
works in mame or not.. as its been a very long while, since I last tried)
I believe I used to use a 27" Panasonic tv, with my Consoles. It was a good size for lightgun games,
standing several feet back from it.