Imo, Vicksburg was his most impressive campaign.
Frankly, it was the most impressive of the war.
A Soviet General who knew what he was talking about said that wars are won by the least incompetent army. He was quite right, whether speaking about the Legions of Rome, the Tumans of Genghis Khan or the Armies of Napoleon. An army moves on its stomach, Grant understood this but Lee & the CS military in general did not. The US did a far better job of supplying its forces in the field and keeping them supplied than the CS. Logistics make the difference between a winning army and one that is not. Whether that failure began at the highest levels of the CS or was just a general lack of understanding is up to interpretation. What is not up to interpretation is that Grant understood the importance of logistics, certainly more so than any adversary he faced on the CS side.
Amateurs study battles & tactics while the professionals study logistics & geography.
Grant understood that the moment you force an opponent to suffer a siege he is done for. Every time he initiated a siege a CS Army would surrender to him.
Most Europeans were rather critical of the ACW as they viewed it as a war between bumbling amateurs commanding howling mobs. Those who actually saw the various armies first hand, however, had a rather different view. To paraphrase an acquaintance from college (another professional soldier who knew what he was talking about) at the beginning of the American Civil War both sides were fielding good fighters; America has always fielded good fighters. But by the end of the War both sides were fielding good soldiers.
Grant forged and shaped the US Army of the West starting with what would become the Army of the Tennessee and his influence would continue to have an impact all the way through the end of the war. The result of his leadership would be the utter & complete destruction of the CS. By the spring of 1865 the CS could field no army capable of defeating a US army facing it.
Was Grant brilliant? No, he never would have claimed he was. He put the responsibility for the victories of the US where they belonged: squarely on the shoulders of those on the sharp end of the spear.
Those who claim 'they had more' therefore they won fail to understand military history. More is not always better, in fact the best armies in history consistantly won against numerically superior foes. Though if they wish to say the CS soldier wasn't half the soldier of the Roman Legions, Mongol Tumans, or French Divisions... well history seems to bear that out.
There are those on this site who would say the US soldier was a craven coward who raped, pillaged and looted his way across the Confederacy and that 360,000 dead US soldiers was a good thing as it was that much less of a plague upon the continent. I see that kind of thing and know full well they have a very poor understanding of history or military matters at all and any claim they have to honor or integrity is self styled... at best.
Bringing the