I wouldn't be so sure. Winning the Revolution and delivering the infant republic was only part of Washington's legacy. Guiding and protecting that infant through the dangerous early years was Washington's most significant accomplishment. Washington, to the day he died, always put that infant nation first.
If the Confederacy had won, Lee would have again turned inward to Virginia (which is about all he concerned himself with during the war as well) and through the early years of that "republic" when the inevitable disputes and dangers would have arisen, Lee would have only viewed them through the eyes of a Virginian. He would not have been the indispensable man of the Confederate States. He would always be what was expected of him by his family legacy --- Robert E. Lee, Virginian.
I have found some aspects of the early years of the United States of America totally fascinating. For obvious reasons the Civil War is seen as the nation's most dire period of time in terms of national unity, and many of the issues discussed in national politics today focus on "the intent of the founders" in Constitutional terms. But I could make a very strong case that the United States as envisioned by the founders didn't even last for five years.
All of the founders' notions of independence, self-rule and Constitutional rights went out the window when the Federal government imposed a tax on whiskey in the early 1790s. This (along with a number of other issues) eventually culminated in the Whiskey Rebellion in western Pennsylvania in 1794. Settlers in the sparsely-populated Appalachian highlands had to cope with poor crop yields, and so it was more lucrative for them to distill their corn into whiskey than to incur the cost of transporting it over the rugged terrain to the East Coast. The imposition of that whiskey tax was a blatant abuse of Federal power (which was enacted simply because the people who were most affected by it had the least influence in government), and it resulted in a serious sense of disaffection along the frontier that remains even to this day (numerous "Run, Eric, Run!" signs could be found all over parts of western North Carolina when Federal ATF agents spent years looking for suspected abortion clinic and Atlanta Olympic bomber Eric Rudolph).
The Whiskey Rebellion eventually ended in the fall of 1794 when Washington gathered a Federal militia to quell the uprising. The Federal troops were gathered from eastern Pennsylvania, Virginia, Maryland, and New Jersey . . . and they were led by a gentleman named Harry Lee.
That's General Harry Lee, the Governor of Virginia -- and father of Robert E. Lee.