Id suggest if you ranked the league in order of best keepers you wouldn't be a million miles off the actual league table which tells you all you need really.
is that not going to be the case for pretty much every position?
The elite GKs can, and do, make a difference. Often heard it said the amount of points the likes of Schmichel and de Gea have earnt United by pulling of quality saves thus securing the 3 points from winning positions.