Here's my observation regarding themes, as in Ghostbusters' theme: It depends on how much you're into pinball. Places I go that have pinball machines AND teenagers, 20's, and 30's yr olds (like theater arcades, barcades, bars with a few games, pizza joints, amusement parks, truck stops? ha) the machines are almost always empty regardless of themes, and I've seen all the themes being talked about. The video dancing and driving arcade machines and air hockey are way more active. So, truly?... Stern must know this and isn't even targeting these age groups, at least not with their "themes", including Ghostbusters. (But maybe with the lame video modes, idk, ha) To be clear, my 21 and 25 yr olds couldn't care less about GB. And for people that keep bringing up their 8 yr olds who love 80's themes... they're pre-adolescents, and it's all about pleasing parents (or lights and sounds) so any excitement over a "theme" is probably more mirroring you, than their genuine love for the brilliant comedic slapstick and cinematography of, say, a Ghostbusters.
Now then for those of us really into pinball, here's what I see... we have lots of choices and can be picky about how we spend our time (and money) on pinball. So... theme is very important. Because brilliant gameplay or not, I don't want to spend time on my favorite hobby being irritated or bored by the theme. I'm actually struggling a little bit with SM over this issue right now.
Theme, alone, can't "make" the game. But it can, alone, spoil the game.