The problem with this is that you are comparing players from different eras, especially players from today (where you can play your game everywhere because conditions today are so similar everywhere) with former eras where you had absolutely drastic differences in courts/speed.
Can you imagine Nadal or Djokovic playing in conditions like this: http://www.youtube.com/watch?v=zXhExBDc-K0
In fact Courier was much more suited for this high-speed low bouncing carpet because of his ultra-short-compact strokes swings (and he had a very good serve and he knew how to volley) than any of todays top-players bar Federer.
Long backswing, full swings at the ball was almots impossible in those fast and low-bouncing carpets from the beginning of the 90s (and obviously in the 80s and 70s and before).
Players that adapted well to those conditions usually had very short-compact strokes (or at least they were able to hit like that when playing on those conditions) and were able to snap the ball almost flat with control and pace (you had no more time to do otherwise).
Put 90s varied conditions into 2000-2010 and we would have seen a TOTALLY DIFFERENT scenario (probably many more different players winning big things, GS and WTF, and not always the same three people everywhere).
WTF from 1997 on was SO MUCH SLOWER (and the rest of the indoor tournaments slowed down as well), but WTF of 2012 has been simply impossible to believe how terribly slow it was.
How can you compare players from the last 10 years with former players when tennis was like a totally different sport (with totally opposite conditions along the year, making it much more difficult for the same good players to accumulate points in "your ranking").
Think it seriously, put Nadal or Djokovic in that court against Becker and they would have had to change drastically their strokes to even have a remote chance of competing there.
Today they don't have to.