I think Mike Clayton's answer has to be the correct one, inasmuch as such a large portion of Australia's prestige, classic courses are linked to Mackenzie's visit.
Bob - you have seen more golf courses than I have, so I respect your view, but DCC does make Tom Doak's Gourmet 30 in TCG, so I suspect he would be at least one well qualified person who would disagree with your assessment.
I was actually at DCC this past Sunday. I promise to post some pictures, although unfortunately the weather was pretty dire so they are not great.
But there is no doubt that the course has a couple of memorable holes, notably 3,5,8 and 17,18 which I think justify its superior ranking.
Mark: South Africa's golfing prowess is down to climate and general sporting prowess. If there was a correlation between GCA and prowess, there would be more good Scots golfers.
Of the list of older courses Tom M quotes, I have played, DCC, Houghton, Glendower and Royal Cape. I don't think any of the last three courses are in any way exceptional, though admittedly I was a total GCA illiterate when I played them, as opposed to current levels of sophistication.
I have never heard it suggested that Maccauvlei or Royal Port Alfred are that good. Humewood especially, and maybe East London, have stronger claims on being notable courses. The 2007 project is to try and bring some photos of those last two to this forum.
When I have some more time I will post separately a few stats on recent golf course development in SA. I think about 26 new courses have been built in the last 5 years or so. These have overwhelmingly been estate developments ( a new development in SA) and at least 80% have been designed by two architects - Gary Player and Peter Matkovitch.
I am not persuaded that many of these modern courses are up to much architecturally, though I think some of them would be worth playing if only for the scenic splendour (eg Oubaai, designed by Ernie Els, which has a Cape Kidnappers type feel from the pictures; Arabella, designed by Peter Matkovich, near Cape Town, and Leopard Creek - in the East, near the Kruger Park, which is supposed to be South Africa's answer to Augusta - at least in the conception of Johann Rupert, who built it. It is a Gary Player design).