Attendees wait in line to see the new Nintendo Wii U controller during the Electronic Entertainment Expo, or E3, in Los Angeles June 7, 2011. Credit: Reuters/Mario Anzuoni By Liana B. Baker Fri Jun 1, 2012 6:23pm EDT (Reuters) - Nintendo Co Ltd has more to prove than ever when it takes the wraps off its highly anticipated "Wii U" gaming console at next week's "E3," the $78.5 billion videogame industry's most important yearly trade show. Gamers and Wall Street analysts alike will be closely watching for the next salvos from Nintendo, Sony Corp and Microsoft Corp - the "big three" of…