So this makes Grant better than them, but it does not make Grant better than Lee. To see who is better, it needs must be a fair fight.
Winning with a huge advantage is less impressive than winning with even odds, or worse odds.
And Lee had the major advantage of being able to fight the entire war on the defensive if he chose, whereas the north had to take the offensive. Had he chose to take advantage of this from the outset and not be so concerned with preserving Richmond at all costs, this would have easily offset the North’s numerical advantages. And it wasn’t numerical advantages that allowed Grant to steal a march on Lee after Cold Harbor, cross the Rappahanpock river unmolested and essentially end the war. Every General enters a campaign with certain advantages and disadvantages. What they do with them is the measure of their generalship.