Rafa would have been #1 earlier but that's about it. No slam domination.
Roger barely 'dominated' RG the past five years I'd say, and Rafa might well have had 3 Wimbledons right now if it weren't for Roger. That would have meant 8 GS titles already and would have surely put him in the list of 'greatest players to ever play the game', imho (and I still think he belongs in that list even right now). And perhaps five years at #1...
Just the raw luck to play in Roger's era, as it is Roger's raw luck to be denied the RG title 4 times by Rafa.