Who is the best US Open Champion?

Best US Open Champion

1. 1.
   
   Roger Federer (2004-2008)
2. 2.
   
   Rafael Nadal (2010)
3. 3.
   
   Andre Agassi (1999)
4. 4.
   
   Serena Williams (1999, 2002, 2008)
5. 5.
   
   Pete Sampras (2002)
6. 6.
   
   Novak Djokovic (2011)
7. 7.
   
   Andy Roddick (2003)
8. 8.
   
   Venus Williams (2000-2001)
9. 9.
   
   Maria Sharapova (2006)
10. 10.
    
    Kim Clijsters (2005, 2009-2010)