Vehicular mayhem. Sexual conquests. Teenagers can experience it all through today's almost-anything-goes breed of video games, primarily among those rated "M'' for mature. The Entertainment Software Rating Board is responsible for that rating system, and this self-regulating videogame industry group has suddenly found itself on the hot seat. Critics say the board's guidance is toothless and does little to help parents trying to protect impressionable children from questionable content.