Sharapova is such a hot and cold player. She has no middle game, if she on she's great, if not she's average. Basically she probably wouldn't have the same amount of slams if there was anyone good around. Serena can't win every slam, but she is the only truly world class player out there. It's like if Nadal was the only world class player (Fed, retired in 2007 and Djokovic and Murray don't exist) Nadal still wouldn't have won everything. Someone else would have won AO 2010 and 2011, RG 2009, Wimbledon 2012, US Oen 2009 for instance. Maybe Soderling or Berdych or Tsonga would have a few slams. Wouldn't make them any better as players.
Serena is now dealing with players who offer her as much competition as people like Tsonga offer Federer. At one time she had henin, Venus, Clijsters really giving her a hard time, but now no-one has the game or guts to stand with her.
Federer, Djokovic, Delpo fan (also like Nalbandian, Dimitrov, Tsonga)