First PS4 exclusive to pass 20m this gen if I'm not mistaken. Uncharted 4 was at 15m last official update, Horizon at 10m last official update, God of War 10m last official update. Considering Sony never announced 20m for those 3, it's probably safe to assume that Spider-Man beat all 3 of them to 20m.
Wasnt there a thread a little time ago that said GOW 2018 had already passed the 20m sales? I take it there was no official source on that then.