very very very hard for me : in the end I went for Murray
I hesitated mostly with Nadal, then with Djokovic.
I don't believe Federer can do it again, it's too hard at that age with such a competition : I just hope he wins 1 or 2 slams (even if what's good for Federer is that they might also neutralize each other and then winning 1 or 2 slams might be enough).
Del Potro can also do it, he has all the tennis potential but I'm more concerned about his physical and the fact that it seems that Wimbledon is not for him.
It's between those 5
Roddick or Söderling
But I think the ATP World Tour final will tell us more