I always think it is funny when people talk about "not even looking at ratings." Ratings are important because, like it or not, higher ratings = higher value this is why Demolition man, made a year after though still wide body, is less valuable than Indiana Jones the pinball Adventure.
It doesn't take anything away from the "fun" of Demo man but, the theme art package etc....well, detract from its desirability.
unfortunately the ratings system is used to inflate game values on Pinside...which makes the market(on pinside) kind of skewed.
If you really want to learn about a pin though...you know, to "compare" it to others you have liked to see if it might be worth buying...use multiple sources like you were taught in school...even then you STILL might trade it in a month
I personally think that Wizard of Oz is in no way less than a top 20 machine but...that is just me being hypnotized by all the pretty lights