Grant served in the west until 1864 and never lost a battle. He out-maneuvered and forced the surrender of two rebel armies. His Vicksburg campaign basically went against every established military maxim on supply and communications channels and wound up cutting the Confederacy in two. Grant's genius was well established before he came east.
Like I said, not taking anything away from General Grant, as he truly was a man for the times, but how much of his success was due to the fact that he also had General William Tecumseh Sherman within his ranks? He was also a man of the times and a true leader, unabashedly brutal, as well as, a military genius.