The Modern Warfare 2 base game's size is 37.4 GB on Xbox One and Xbox Series X|S. You'll need another 17 GB for the campaign, 8 GB for the multiplayer, and 3.9 GB for Spec Ops.
Call of Duty: World War 2 has a 45.14GB download size on the Xbox One, 56GB on the PS4, and a whopping 90GB on PC. Given the colossal Call of Duty: World War 2 file sizes, Activision has allowed those buying the game digitally to preload the game right now.