EM displays ruled the earth until the mid-70's, and DMDs have had a 24-year run since Checkpoint appeared in 1991. But from 1975 ("Dyn O' Mite") to 1991 ("Bride of Pinbot"), the new "Solid State" games with numeric and alphanumeric displays carried the torch for 16 years. Yes, DMDs are solid state too, but there's a long tradition of calling pre-DMD pins with digital scoring "Solid State". That won't change unless a better term comes along.
My first pin was a 1980 Black Knight, and my memories of it are marred by lots and lots of work and instability. When I bought my second pin, a 1988 Space Station, I thought I was done with the early 80's as a collector. The sounds and diagnostics were miles ahead of my BK, and there were VUKs and flashers, cool! And yet...if you look at my SS collection now, I'm very heavy on the early 80's. Here's how I break them down into "sub-eras". This is just my view, and I'd love to hear other ways people group their SS pins.
1977 - 1980: The Golden Years
Paragon, Mata Hari, Skateball, Trident, Magic. These are all relatively new to my collection, but I've played them a lot at pinball shows. They're simple but addictive pins. Some have sounds that emulate chimes (or actual chimes), while others have great sci-fi noises.
1980 - 1981: The First Talkers
Embryon, Medusa, Fathom, Black Knight, Lightning. Great artwork and layout are still the focus, but now speech makes deeper rules possible. Background sounds accelerate to let you know when you're doing great. By this time, most games either have multiball, or are full of cool gimmicks (e.g. Medusa).
1982 - 1984: The Lean Years
Andromeda, Time Fantasy. Gone are the speech and other advanced features of earlier games. In a way these pins seem like throwbacks to the Golden Years: great art and simple gameplay. The goal was to stay relevant while videogames took over the arcades.
1984 - 1990: The Comeback Years
Space Station, Hot Shots, Whirlwind. I'd define Space Shuttle as the first pin of this sub-era, since it got people excited about pinball again. Speech was greatly improved, and ramps became a "must have". Cool new features like kickbacks, VUKs, alphanumeric displays and Diamondplate made the older pins seem antiquated. But at the same time, beautiful mirrored backglasses gave way to cheaper translites.