Are you using HD video (component cable and HDTV settings)? from here:
Some Virtual Console games default to displaying 240 lines of video. Some HD TV's are unable to display a signal with only 240 lines. Try the steps below to set the Wii to output 480 lines of video, which may solve the problem:
- While on the Wii Channel Menu (main screen of the Wii), connect a Nunchuk to Wii Remote.
- Select the Virtual Console game from the Wii menu, then select "Start" to begin the game.
- When the game starts, press the Home button on the Wii Remote. (In many games, the music can be heard when the game starts.)
- Select "Operations Manual" from the Home menu.
- Press the Z + A + 2 Button simultaneously (the Z Button is on the Nunchuk). A sound will be heard if the button combination has been entered correctly.
- Close the Home menu. The game should now display correctly.
Note: You will not have to do this the next time you play, as the Wii console will remember these settings.