I've been a huge fan of U.S. Grant as the greatest general the U.S. has ever produced in my opinion. Others who actually knew him regarded him highly as well:

"When hearing Grant referred to as a "Military Accident," with no distinguishing merit, one who had achieved success through a combination of fortunate circumstances, Lee responded by saying, "Sir, your opinion is a very poor compliment to me. We all thought Richmond protected, as it was, by our splendid fortifications and defended by our army of veterans, and could not be taken. Yet Grant turned his face to our capital and never turned it away until we had surrendered. Now, I have carefully searched the military records of both ancient and modern history, and have never found Grant's superior as a general. I doubt his superior can be found in all history." -- General Robert E. Lee, commander of the Army of Northern Virginia


"I'm a darned sight smarter than Grant; I know a great deal more about war, military histories, strategy and grand tactics than he does; I know more about organization, supply, and administration and about everything else than he does; but I'll tell you where he beats me and where he beats the world. He don't care a damn for what the enemy does out of his sight, but it scares me like hell." -- Gen. William Tecumseh Sherman