Quoted from ExtremePinball:

Agreed, all things being equal. The problem is that nothing is equal. Whether the lineup is comprised of 2 pins, or 200 pins, there will always be high earners, and there will always be low earners. Additionally, some machines earn more, or less, in different locations. By this I mean different locations within the same arcade, or even a different position in the line-up itself, as well as different locations out on the street. Proper game placement, as known in real estate, relies on location, location, location.
While you suggest GOT & TWD are the go to pins for revenue, I have both of these in my line up and they both get smoked by IMVE.
However, this may not necessarily be the case in any other location. Case in point: I have 4 pins next door in the Fun Dungeon Arcade at Excalibur Hotel & Casino. IMVE, South Park, Avengers, & Transformers. Of the 4, IMVE is the lowest earner. Go figure.