One of the coolest feature I thought they added, was the "host shifter" thing. On PS3 & 360 LIVE, if the host of a match, quits during the match, the game ends, which is a really bis p!ss off
But, on the Wii version, the game will not end if the host leaves the game, so that's a +1 for the Wii version.
True, COD4:MW is over 2 years old, but I'm sure it's going to surpass the WAW version, cause COD4 is an epic FPS, and has been a long wait for Wii players.