Oldest system, by release year its my Hong Kong 6 Switch Atari 2600. Local guy was selling it and it was in immaculate condition. Dust cover on the system, with boxed games.
At the time I was selling games and systems, so I kept the system and 2 games for myself. Don't use it much since its a 2600, but I have it on my shelf.
Oldest system I own is my GBC, had it since before my youngest sibling was born and I still have it today. Obviously doesn't get much use since GBA SP, but I still keep it around.