I put together the results for the last 4 slams for most active slam winners or number 1s (I excluded Schiavone, Stosur, and Venus, sorry, I forgot!). I wanted to get an idea of their consistency at slams.
In order of number of slams:
Serena
2011 French Open: N/A
2011 Wimbledon: 4th round (l. to Bartoli)
2011 US Open: Final (l. to Stosur)
2012 Australian Open: 4th round (l. to Makarova)
Clijsters
2011 French Open: 2nd round (l. to Rus)
2011 Wimbledon: N/A
2011 US Open: N/A
2012 Australian Open: Semis (l. to Azarenka)
Sharapova
2011 French Open: Semis (l. to Li)
2011 Wimbledon: Final (l. to Kvitova)
2011 US Open: 4th round (l. to Penetta)
2012 Australian Open: Final (l. to Azarenka)
Li
2011 French Open: Win
2011 Wimbledon: 2nd round (l. to Lisicki)
2011 US Open: 1st round (l. to Halep)
2012 Australian Open: 4th round (l. to Clijsters)
Kvitova
2011 French Open: 4th round (l. to Li)
2011 Wimbledon: Win
2011 US Open: 1st round (l. to Dulgheru)
2012 Australian Open: Semis (l. to Sharapova)
Azarenka
2011 French Open: Quarters (l. to Li)
2011 Wimbledon: Semis (l. to Kvitova)
2011 US Open: 3rd round (l. to Serena)
2012 Australian Open: Win
Wozniacki
2011 French Open: 3rd round (l. to Hantuchova)
2011 Wimbledon: 4th round (l. to Cibulkova)
2011 US Open: Semis (l. to Serena)
2012 Australian Open: Quarters (l. to Clijsters)
I had the feeling that Sharapova was the most consistent, but I wasn't aware at how close Azarenka was to her; I'd be willing to call it pretty much equal between them, due to the unfortunate (for her) meeting with Serena in the 3rd round of the US Open. Clijsters hasn't done well, but I'm inclined to give her a pass for injuries; she won both slams before the period I chose (last person to win back-to-back slams? Serena with US Open 2008 and AO 2009).
So, what does this all mean? I really do think that people dismiss the chances of Sharapova winning another slam at their peril. Granted, she played terribly in both slam finals she was in, but she and Azarenka are the only ones who have consistently gone deep at slams over the last year.
The biggest knock against Wozniacki was not that she didn't win a Slam while #1, but that she didn't reach a final while #1.
