Hm. Still looks like some kind of an issue with deinterlacing, except for the part where your Wii is set to 480p, and it just looks like brightness differences instead of combing. Hm.

See if the Sony TV set has any options for deinterlacing modes. They might be labeled things like "film" or "video". See if changing those fixes it.

Is the signal from the Wii passing through any sort of intermediate switching system, or are the cables running straight to the TV's component inputs?

If your DVD player looks fine (and it's using component video too), try swapping inputs between the DVD and the Wii at the TV end. Also try swapping cable sets completely (if the Wii and the DVD are near each other, you can do this by swaping plugs at their end).