Originally Posted by DuckieHo
Virtually all Windows games are 32-bit applications.
All desktop 32-bit Windows applications should all be optimized to run on 2GB. 2GB is the maximum memory an application can have access to a standard 32-bit Windows OS. The other 2GB is reserved for the kernel. If you enable the /3GB flag, a 32-bit application can use up to 3GB but leaves only 1GB for the kernel. Developers know this so they design their games to run in 2GB.
Basically, do not expect games to use more than 2GB until there are more 64-bit games.