Juve are in talks over a €100m deal for Ronaldo.
"For Italian football it would be like winning the lottery," Vieri said on Bein Sports.
“People don't talk about Serie A much abroad, because there aren't the superstars there were in the past. Ronaldo would revitalise it.
“Even I would be more motivated to watch the league, every Sunday the world would be wondering what Juventus did and how many goals Cristiano scored."