Five eras for me.
EMs from the early 50s to late 60s
Early Solid State with Stars and Skateball
Later Alphanumeric with Earthshaker
90s DMD with HS2 and Dirty Harry
Future of pinball with TNA. I mean "welcome to the future"
Used to have at least one flipper game from every decade from the 1940s on, but decided I'm not running a museum here.