It was Grant who dispatched Sherman on his march, and the Union forces were stymied until Grant arrived on the scene to command all Union forces. I don't disagree that the Union had more men and materiel, but offense requires more. Grant was relentless and his genius lie in stubbornly pressing his advantage. He showed earlier determination and skill at Shiloh and Vicksburg.
I agree that Grant was very good commander, but I don't think he was on the level of Lee.
Critics of Grant also neglect the way Grant turned a disadvantage to an advantage in the East. Prior to Grant's arrival all Union offensive campaigns were culminated by a single battle (where Lee's forces would send them reeling in general retreat) -- nothing lasting was achieved for the casualties expended. Grant, though he also lost battles to Lee, managed to maintain the general offensive despite his losses. No other Union general had that moral courage.
Lee may have been the better 'Napoleonic General' but Grant wasn't fighting a Napoleonic war anymore.