Call Of Duty: Modern Warfare 3 is surpassing 200GB in size, and Activision has explained that this is thanks to the increased amount of content  available in this entry. To compare, Call Of Duty: Modern Warfare 2 was 125GB on PC.
Minimum Requirements
Recommended Specifications
Memory
8 GB RAM
12 GB RAM
Hard Drive Space
175 GB
Network
Broadband Internet connection