According to Nintendo Inc., Showtime Championship Boxing will be one of the latest video game releases in the new and wildly popular Nintendo Wii.   Due to be released by the end of the year, probably by Christmas, the Showtime Championship Boxing video game will be available for the Nintendo Wii and the new Nintendo DS lite, a hand held, touch screen and wifi video games system.   Although the Nintendo Wii is not yet available in HD as are the Xbox 360 and the Playstation 3, the Wii's popularity comes from the ability for gamers to interact their entire body with the screen and video game.  Gamers will literally punch at the screen when playing the new Showtime Championship Boxing game.  The Wii's popularity also comes from the fact that it is hundreds of dollars cheaper than the Playstation 3 and Xbox 360.