well it's more accurate to say that games are not as Linux friendly as they are Windows friendly. Otherwise Linux-based games work just well as Windows as long as they are native linux versions. But that is being a nit-picker.
I do not beleive that they released a native Linux version of CoD, although they have Linux-based dedicated servers. I could be wrong.
What you would use to play it isn't realy technically emulation. What it is is a Win32 + DirectX implimentation on Linux.
Win32 is microsoft's programming interface for their Windows operating system, this Cedega (formally WineX) is a behave-alike that is designed to run in Linux. So it's much faster then emulation, however it's not as fast as MS's native version.
Games that are DirectX-only will run with about a 10-30% hit on performance. Games that are OpenGL will have less of a hit, and many games (especially Quake-based) say that they require DirectX, but for the actual game they are OpenGL, they use DirectX for the sound or the menus or something like that.
Cedega costs money, last time I checked they were 5 bucks subscription for at least 3 months, but that was a while ago.... So it may have changed.
for game compatability they have a game database that is searchable online.
http://transgaming.org/gamesdb...iew.mhtml?game_id=3200
You have unlimited downloads and it's fairly easy to isntall and take care of.
But it's not linux-native.
Another problem is hardware. If your running a ATI card it'll be difficult compared to running a nvidia card. But if you can handle this Linux is still on your horizon.