Given that you can make any game easier/harder based on the physical setup, I usually tend to think about the complexity of the rules, and the opportunities to progress through the game in different ways. A lot of games tend to boil down to "do this one thing" to score well. There might be other things on the playfield, but if you want to do well there was one overwhelming strategy. That's why I always gravitated to games with deeper rules, since I like having balance/options, and having more "new" things to discover. That's one of the reasons I bought TSPP as my second game-I've owned that thing for 14 years I think, and I've still never seen the end of it (and probably never will). It's not a super difficult layout, but there's a lot of stuff to keep in your head on how to play it. You have stackable modes, multiballs, and frenzies, and some mini wizard modes that are achieveable for mere mortals that are a lot of fun, but have their own bespoke rules. It might still be one of the trickiest games to wrap your head around. If you want recent examples of playfields that will kick your ass, Walking Dead is a good suggestion, as is BKSOR (not as much rules depth on that one, but it will make you better at reacting to stuff). Easy games... DE Star Wars is super easy to just shoot the ramp over and over again, and Gottlieb Super Mario Bros is one of the most boring games I've ever played. Addams Family also gets to be really easy/repetitive when you know what you're doing. As for newer stuff, the Beatles is a pretty simple game that's still fun to play and feel like you're doing something cool.