As an Atlantan I have never understood why golf, on average, is so "below average" here. It would seem to me that the land could have produced some very interesting sites but again, Atlanta has little in terms of architectural interest.
To me it has a lot to do with when a city was developed/grew.
Most older cities have ODG courses that have the advantages of maturity, intimacy,less housing based (the bane of Atlanta) and well....good architecture
From all I hear Chris you've certainly bucked the trend in Atlanta 
Hah. Very kind of you to say. 
To my untrained eye I see Atlanta as nicely flowing land with countless locations full of mature, deciduous trees, creeks, streams, rolling land...
Too many courses here are simply real estate "lot enhancers" but even the core courses here don't compare to courses I have been fortunate to play up North. The entire scale and "feel" of golf up north just seems different. I like pretty much everything else about my South, but for great golf courses we have to travel 
Chris,
Atlanta has a few courses going for it. Peachtree is one of the best in the world!
Nigel,
I too love Peachtree and it is my choice for best day of golf in Atlanta for sure. The first hole is one of the best openers in golf. The superintendent there is a friend of mine, William Shirley--he was at my club many years ago before he became famous
and his daughter Maragaret is the current US Mid-AM Women's champ.
William has Peachtree has one of the finest conditioned courses I've ever played. He has firm, fast bent and the zoysia fairway/bermuda rough contrast is simply awesome.
Anyway, while I love Peachtree I could not vote it one of the best "in the world" if by that you mean top 25 of all golf courses in the world. The routing is excellent, it is a great walk in the park, the "experience" is near perfect, but there are too many similar blind, uphill shots for my taste. Holes 8 and 9 parrot 17 and 18 a bit too much for me and are all part of that uphill, blind approach that I think is a tad overdone.
Par threes are very good though 11 is a tad plain for my taste.
Par fives are OK. #2 has a unique green, #5 is a bit awkward off the tee, #10 is fun but the approach is kind of bland. #16 is very good.
Again--lots of uphill shots to greens that have a lot of "blindness":
#3, #5, #8, #9, #10, (even #11 a little), #16, #17 and #18
Don't get me wrong, Peachtree is awesome but despite my fondness for it, I just could not put it among the "best in the world" if all we are talking about are the golf holes. As a golf club and taking the entire experience in toto, then yes, I would certainly vote it "world class"