Sun Tzu likely wasn't an individual. The 13 great chapters in his book are probably an amalgamation of knowledge from a great variety of leaders from 500 to 250 BC. This doesn't lessen the brilliance in the text. Unlike Clausewitz, who would follow almost a millennium later, Sun Tzu is nuanced, less absolute and more practical for today's matrixed world.
That said, are the Sun Tzu quotes a little overused? I've used them in at least three exec level presentations and you can't go more than a couple slides in any corporation's internal sales decks without finding one. Reading the Sunday NYT, there was an ATT advertisement with a Sun Tzu quote. Maybe the "new" ATT is using Sun Tzu as a guide. The "old" ATT sure wasn't and would have benefited if it had followed Sun Tzu's advise earlier: "You should not linger in desolate ground."
Maybe Sun Tzu is now the universal strategy standard. If everyone is following his dictates, though, is it time to find another inspiration? Maybe there is some obscure leader out there who beat Sun Tzu in 200BC and I can start using that strategy. Or more likely, like everything else, it comes down to execution. People quote Sun Tzu, but can't execute his vision.