Quoted from AlexG:Going back 20 years there is only one answer, Star Wars Episode 1. There can be no debate. It was a hugely anticipated movie and a brand new pinball platform full of potential.
What we got was a lousy movie full of uninspired special effects, a symmetrical play field with an uninspired rule set and the game that was directly responsible for the death of Williams pinball. That game was the start of the lowest point for the industry and nearly killed pinball.
No way. SWE1 had very little to do with the demise of Williams or pinball in general. In fact it was the other way around...the decline of the pinball market is why SWE1 didn't have more development and Williams closed -- a decision made before SWE1 was even released. In fact just looking at the Star Wars licensed games I would rather play SWE1 than SWT or maybe the Data East SW...if the SWE1 movie clips were able to be skipped faster.
If you're talking about disappointment from hype/expectations and cost (new), I would say some of the newer games. Mustang probably gets my vote, followed by WWE. Expectations were low in the early 2000s so I wouldn't pick those.
For the theme/license possibilities, probably BDK for me.
For how the game looks? WOF, because some of the stuff you see literally isn't coded.