Firstly, Federer has a similar gap (Wim 03-12). Djokovic has to surpass Fedal in that regard, else he is stuck on 13 at most :P
Secondly, Sampras has the biggest gap in the Open era, obviously (shame on you for forgetting). 12 years between USO '90 and USO '02. That's really tough to beat. A good reminder that Sampras continues to hold a couple great records and statistics that the big 3 haven't sniffed.
I stand corrected. Sampras' record will not be beaten, I don't think. Jaw-dropping, really. Shame on me for forgetting.
I shouldn't have forgotten Federer's gap, either. It was commented on when he won in 2012.
In my defense: it was early in the morning and I was multi-tasking.