A great general like Lee, with good troops like those of the Army of Northern Virginia, cannot be defeated without a willingness to incur losses. Furthermore, great generals are often very aggressive, and are sometimes over-bold and take heavy losses as a result. You will see this phenomenon abundantly present in the campaigns of Frederick, Napoleon, Rommel and Lee (for example, Pickett's charge and Malvern Hill).
You're silly, if you think Grant was anything but average, in a group of horrible below average peers. The only thing that could make Grant look good, or gives the appearance of competence in the "operational art" is that most all his peers on the Union side were much worse.
Please don't use Vicksburg as an example, it was a seige of overwhelming superior land and naval forces at the disposal of someone who could apply basic principles of warefare.
So you need to hit the history books other than those unfortunate books read in our elementry and high schools.