Man, I don't know why but it's been my Star Wars pro. I've gotten a couple of really great new games since I got it and it's still my go-to.
It's so stripped down and a bit rough around the edges, and the majority of the games kick my ass so hard... but then I get a bunch of stacked multiballs and manage to move the multipliers around successfully and all of a sudden I'm blowing things up and it's totally great! And then I suck again and can't help but continue to chase that high.