I suppose this is based on Lee's supposed remark about Gettysburg:
"If Stonewall had been here, we'd have won.", or something like that.
We know nothing of the never was; but personally I don't think the South could ever have "won" the civil war without some kind of fluke circumstance occuring, i.e. some antagonism with Britain over searching cargo vessels breaks out into hostility, or some other incident.
The North simply had more resources; and the south never really "brought the battle" to Northern soil, Gettysburg aside.
For what it's worth, I also believe the North had a superior moral force; and that it was a good thing for the world that they did win.