I'd say the golden age was probably the 1970s. Pinball became legal in so many places where it hadn't been before. Three inch flippers were becoming the norm. Tommy had come out. Video games weren't a threat yet, but more of an added attraction to get people in to arcades to play pinball. Solid state games appear. Wide bodies. Talking pins. At least four large American companies, plus numerous foreign operations, were building more pins than they ever had before.

It was a golden era until Space Invaders in 1979 and Pac-Man in 1980 start taking in all those potential pinball quarters. Smaller footprint, less maintenance, shorter game times, no replays, and things start looking bad for pinball. At least till Space Shuttle and the mid-80s to early-90s resurgence, the silver age if you will.

I still stick with the 70s. I think the enjoyment was pretty high when so many different pins were coming out at once. They were everywhere, the different manufacturers were constantly trying new things to compete with each other, and the general health of the industry made things better for the average player. If enjoyment just means games with deep rules, then the 90s or today would be the golden age. I just think the best time was when it was ubiquitous and flooding with new ideas from lots of places.