My bets:
PlayStation 5 vs Nintendo Switch'19 (19.2M):
Winner: Switch 2019.
PS5 stock issues.
PlayStation 4 vs PlayStation 3'16 (670k):
Winner: PS3 2016.
PS4 in Japan sold 70 until now, even without PS5 stock issues.
Xbox One vs Xbox 360'16 (390k):
Winner: Xbox One,
still good machine for gamepass, or even cloud
Xbox Series vs Xbox 360'08 (11.1M):
Winner: Xbox Series
Series S sells when the others dont have stock
Nintendo Switch vs Nintendo DS'10 (20.5M):
Winner: Tie.
I expect Switch to sell around 20.5