Quoted from KingVidiot:

I also have a theory as to why Medieval Madness, Attack From Mars, Adam's Family, and Monster Bash have stayed at the top: Nostalgia
Lots of pinsiders holding on to mint games from 25 years ago trying to protect their investments too. Heck, once Godzilla starting getting such rave reviews, I saw a flood of new glowing reviews for MM, AFM, MB, etc.... odd right?
Nostalgia is a hellava drug. Ask yourself what your favorite band is - let me guess, you heard them when you were in your teens or early 20s? Odd. Literally every single person I've ever met discovered their favorite bands of all time when they were kids.
Godzilla doesn't have nostalgia yet. Nor does Elvira House of Horrors, or Dialed In, Rick & Morty, Total Nuclear Annihilation or Stranger Things (theme based on 80s nostalgia, but that's not exactly what I mean here).
Most people probably believe the best pinball machine is the one that started or cemented their love affair with pinball, and since pinball hit a serious streak in the mid 90s, it's no wonder that today's 40-50 year olds love those machines... they were teens and early 20-somethings back then.
Are they still great games today? For sure, but as someone who only got into pinball in the last 3 years, I find those 90s pins to be extremely shallow and clunky playing, compared to tables like Elvira House of Horrors, Godzilla, Avengers, Munsters, Tron, Stern Trek, etc. I find that Stern games just shoot so much better than anything from the 90s. I love the themes from those older games, and the callouts and music too, but they just feel like exactly what they are - arcades designed for short, shallow, fun experiences to get more quarters in the machines.
I played mostly arcade video games in the 80s and 90s. I have tons of fond nostalgic memories of them. Do I think Double Dragon is a better brawler than Yakuza Zero? Of course not... but some people actually think so.
Nostalgia. It made millions on that turd of a Matrix movie recently. It's so powerful, it should almost be illegal.
Today, the home market is as big, if not bigger than the arcade market. The games have been designed that way for well over a decade now, and it shows. Deep rulesets. Long tail support for code.
Medieval Madness, Attack From Mars, Adam's Family, and Monster Bash are all amazing games, even by today's standards, but they are most definitely shallow, but that's okay. I still play Double Dragon and Final Fight now and again too, because sometimes shallow, simple fun scratches that itch more than something you have to think too hard about. I'm looking at you, Avengers.