I'm going to echo what Hilton said, every location is different. I have two locations, one is a family oriented pizza restaurant, the other is a bar and grill. What is popular at one is not necessarily popular at the other. You'll have to learn what your customers want, it will be different than what anyone here suggests.
That being said, here's what has been popular for me:
Both locations:
Iron Man - this has been extremely popular at both locations. Hands down my best earning game over all.
Addams Family - Doesn't earn the most, but is consistent and people want to play it
Theatre of Magic - Just a great theme that appeals to many
Medieval Madness - Does pretty good. Priced at $1 play which lowered its earnings at the pizza place because kids don't want to pay $1. Does fine in the bar at $1/play.
Doctor Who
Funhouse
Pizza restaurant:
DE Star Wars
Jurassic Park
World Cup Soccer
Ghostbusters - Has done VERY good
Batman Dark Knight - popular with kids
Bar:
Metallica - Has done much better than I imagined
Flash Gordon - priced at 25 cents/play
What has not done well is non-DMD games priced at 50 cents/play, especially if you have DMD games also priced at 50 cents/play. The exception to this is Funhouse. It earns well next to DMD games. Examples of non-DMD games that have NOT earned well:
Whirlwind
Earthshaker
Fathom
Space Station
These games would probably have earned me more money if they were priced at 25 cents/play. The next non-DMD game I'm putting in is Grand Lizard, it will be priced at 25 cents.
I always keep one game priced at 25 cents/play. This is VERY popular. It is usually an older solid state such as Tri Zone, Firepower, Flash Gordon, or an EM. I'll often earn as much with the quarter game as a higher priced game because kids will drop a quarter time and time again but are hesitant to put 75 cents in a game. The 25 cent game also attracts casual players that are intimidated by complex and complicated looking games. You could make an argument that I'd earn more by having a higher priced game in this spot, but my data backs up the fact that a 25 cent game will usually out earn an non-DMD game priced at 50 cents. And they sometimes out earn a 50 cent DMD game.