Theres a difference between a "demake" and a "downport"...
A demake is when you take something, and remake it in a simpler style. Generally these are fan projects such as Super Smash Land (Smash Bros demake for Gameboy), Halo 2600 (Halo for the Atari 2600), NES Styled Mega Man 7/8, Bit of War (NES God of War) etc...
A downport is a port to a weaker console, and if you think about it, many console games are downports from the PC version. It is just a matter to moving the game to another console and adjusting the graphical fidelity (and various other things). The reason this is done is obvious.
PS: What is wrong with CoD on Wii? I had a ton of fun with World at War... IR Pointer is amazing for FPS games.