Quoted from rai:
press and hold the start button should remove all the current games started but will start a new game. I don't know if there is a way to go back to attract mode.
Also this is a setting in the menu that may be turned off if you don't like to restart games.
I believe they just added that feature in the new Game of Thrones code. You hold the left flipper button and the start button and it will end the game and go back to attract mode. That is the only game I have heard of adding it, but I expect it will be added to other games eventually.
I also believe this is a feature that can be enabled or disabled in the options menu.
It's a nice and simple option....now they just need to make it so setting a game in tournament mode makes it so the scores are always shown on the screen after a game. A score keeper doesn't care who is the "whoopdie doo champ" when they are trying to record scores.