wind style is the best. when it hit the human path, there was nothing left. and it's cutting effect makes it pretty much impossible for ordinary ninja to survive, you can't regenerate after having your chakra vessels cut. so even tsunade, orochimaru, and kabuto wouldnt survive a clean hit from rasenshuriken.
after that, i think earth or lightning style would be the best. earth has the most raw power, so it would be the most powerful rasengan, while lightning would be the most piercing power, it would be like a raikiri on steroids, both would tear a hole through the opponent.
personally, fire's burning effect and water's crushing effect pale in comparison. BUT, they could be used in a combination technique with naruto's clones like he did with yamato vs kakuzu, we've already seen the water version, which beat a wind and fire combination, and we know that wind/fire combinations work very well with each other.