The early SS games are the pinnacle of pinball IMO. Gameplay, theme, artwork, sounds. They really are the total package. You're really splitting hairs when deciding between Stern, Bally & Williams titles from that era (and even the criminally underrated Gottliebs for that matter). My favorites that I've been lucky enough to play:

BALLY: Centaur, Fathom, Mystic, Flash Gordon, Embryon, Nitro Ground Shaker, Harlem Globetrotters, Skateball, Viking
STERN: Quicksilver, Nine Ball, Star Gazer, Catacomb, Cheetah, Dragonfist, Big Game, Ali
WILLIAMS: Barracora, Cosmic Gunfight, Warlok, Defender, Solar Fire, Time Fantasy
GOTTLIEB: Alien Star, Countdown, Punk, Eclipse, Striker, Black Hole, Devils Dare

Good luck finding some of these, let alone finding them available for purchase

In my general opinion, here's how I summarize them:
BALLY: Incredible artwork
STERN: Incredible gameplay
WILLIAMS: Incredible sounds
GOTTLIEB: Incredible parts

They may come & go through your collection since there are so many incredible titles across all the manufactures, but the Sterns never leave. They're just too good IMO.

This^^^

FG is fricking brutal. It is supposed to be that way. Ultimate risk vs reward shots, always struggling to get the ball under control. And it's the only game I've ever regretted selling. Set your dips to conservative settings & prepare to be frustrated. It will make you a better player.