I don't know if anyone has looked at the Google trends for Mayweather Jr. and Pacquiao. It's predictable, but interesting nonetheless:
http://www.google.com/trends?q=mayweather%2C+pacquiao
Both fighters experienced their first major growth in popularity (according to Google searches) in their fights with Oscar. Obviously there's a lot more Pacquiao searches coming from the Philippines, but I think Pacquiao edges out Mayweather in search popularity in the US as well.