He was unlucky in the sense that he had to coexist with two of the best players ever to play the game. In order to win Grand Slams consistently, a great game is not enough. A player needs incredible mental strength and confidence. In 2007 Novak showed the world(and himself) that he had the right attitude and the game to be a champion. He reached the #3 spot, but Grand Slams proved elusive for him, they are at a different level. In 2008 he managed to play a fantastic Grand Slam in Australia, but he didn't have the maturity to keep that up day in day out. He was only 20, too young.
But kudos to him for not getting depressed: he kept his #3 ranking and kept dreaming, and kept working and improving...Until he was ready...
In the end the bad luck that he had to coexist with the greatest players, he turned into good luck: he used it to become the player he now is.
I'm hoping that he'll remain injury-free for a long time. Now is his time.