Some guy on the IGN board better explained what the Wii version does in 3 simple steps...
Step 1: Original Image
Step 2: Wii's 16:9 option stretches the image vertically.
Step 3: Your TV stretches the image horizontally to fit the screen
Resulting in a blurrier, jaggier, but larger image... Exactly what you'd get by playing in 4:3 with your TV set to "Zoom"...
What I don't understand is how so many different reviews could label it "True 16:9 widescreen"... Kinda lame... And misuninformeducating...