I’ve used the word machines because in the UK at least retro gaming is as much about computers and electronic games as it is consoles.

So my favourites:

1970s Binatone Pong clone built into two controllers. One held batteries and the other the chip and RF modulator. (Close second was an LED pool/snooker electromechanical game I can’t remember the make)

1980s ZX Spectrum. Just excellent gameplay (see Head Over Heels, Batty, Glider Rider etc)

1990s DOS Games too May to list

2000s GameCube. At the time under-rated but now appreciated for some excellent games

RetroReversing is a really cool site hosting loads of content about decompilations, source leaks, information on ROM formats etc.

It's a fantastic resource for finding information about how games tick!