I've decided to start in on the voluminous task of rating all the machines I (can remember) playing, and am trying to calibrate my ranking before starting to rank everything (otherwise, you know, the tendency is to rate everything above average.)
Which brings me to the question: what is the worst pinball game you've ever played? Because you need to have a bottom as well as a top machine. Picking a top one is not a big problem, other than trying to pick among many favorites.
Assume it's in working condition and has no defects other than the ones created by its designers and manufacturers. You may adjust by era. Think: bad rules, weird layout, boring theme, poor artwork, design errors leading to poor gameplay, and in general a complete lack of fun.