Seeing as your in the US, the price difference is significantly less between 90s titles and modern titles compared to Europe.
Personally I always recommend Ripley's believe it or not (RBION) as someones first game. It is a easy game (read: longer playing) with a fun theme and very loaded and GOATed layout (Pat Lawlor is my favorite designer). The rules are not cumbersome to understand for a beginner, but it has a lot of hidden depth and achieving the wizard modes ('1cc' of pinball, in this case reaching Atlantis) is pretty freaking hard on default settings. Took me over a year. Personally I think this game has the best rules ever made, accessibility:depth ratio wise.
Other great options are
- World Cup Soccer 94. Great layout, fun toys/gimmicks and good rules. Just saying, but the 'GOOOOOALLL' announcer is the guy from NBA Jam

- Sega Baywatch. Fantastic packed layout, no realy gimmicks but all pure pinball, good rules
- The Shadow. Also a fantastic (timeless) layout and a really fun upper playfield. Hard game tho
If you can stretch the budget, get a Stern Pro. Especially if you want to avoid maintanence (and they tend to play like new because it's not 30 years old). I'd recommend Deadpool, Dungeons & Dragons (cool rpg mechanics) or Jurassic Park. They are considered as great games, with the cheap version (Pro) being preferred over de Premium.
While there are a lot of games I would say, avoid owning them in small collections, my mantra is: you can always sell the machine and buy a different one if you don't like it. Pinball sell easily (if priced reasonably)
If you let me know your budget, I can give more precise recommendations.