Share your choice for pin for short term replay and long term replayability. These can be two separate pins.
By short term replayability, I mean the game that best delivers that "just one more game" factor. You start playing, an hour or so passes you've been playing the same pin over and over without getting bored.
By long term I mean a game that has lasting appeal, you can always come back to it, because you enjoy the fun experience, there might be many ways to play. It doesn't matter if you've gotten wizard mode, the game is always entertaining, and works as a a standing piece in a collection.
Short-term replay: The Shadow - There are so many way to play the pin for scores, it's relentless but fair and I always feel like I'm just about there (completing the battlefield, making most of the modes, barreling through a vengeance chain)
Long-term replay: Attack from Mars - There is great flow, intuitive, somewhat relaxing but challenging, iconic, fun pin experience. Central target, many multiballs, great callouts, theme art. Whitewater would be a close second. I like how WH20 is really a ramp target game, intuitive, play the field, focus on and hit lit ramps, but there are opportunities to work the rules in different ways for a high score.