@T.A JONES
You may be right, only time will tell...I admire and respect your passion for sure!
To me It really doesn't seem that there is a clear leader in the C+C comparison (In a few random samples I have seen wild swings in the Civ4:Civ3 C+C numbers from 132:67 to 61:92 and many points in between) It will take some time for the numbers to settle down and for a clear picture to emerge. Anyway I don't want to keep quoting statistics as they can be used to prove anything

especially when they are just snapshots and the environment is too dynamic for controls etc. I just felt it was a little early to declare Civ4 DOA based on the few data points available!
My impression is that when Civ3 came out there was really little opposition as far as modding went since Civ3 was clearly an improvement over Civ2 (with the exception of the event files, why did they drop those?) but even so it took time for the Civ3 community to surpass that of Civ2.
Now when Civ4 came out there was a very strong and vibrant community around an existing product and so it had to compete for modders...and of course people are always more comfortable with what they know! The Civ3 community took years to get to where it is now, we should probably give Civ4 2-3 years at least before we try to draw any conclusions.
My own experience as a developer is an interesting analogy here; I tried Java (the new wave) and could develop using it just fine but for some reason I just prefer coding in C++ (the established leader) and would always choose that if given the option. However new blood seems to prefer Java, go figure!
I do happen to disagree with you on the game mechanics and having studied the SDK in depth I believe there is very very little that could not be changed if desired. It's simple, I choose to play Civ4 because I prefer the base game mechanics and to mod Civ4 because I am familiar with the technologies involved. Not that it doesn't have plenty of warts, for example I really dislike

the Civ4 WorldBuilder and wish it were a standalone tool!
Still, I suspect there is plenty of room for both products to coexist for some time to come and a lot will depend of course on the direction Firaxis takes Civ4 in future expansions.
( By the way which do you prefer, classic Trek or Next Generation? 80's BSG or Moore's 2004 reboot? Paper or plastic? Connery or Moore? Civ3 or Civ4?

Don't answer these, at least not here, I was just drawing some more analogies. Most of these come down to individual preferences. Personally I have favourites of course but I can enjoy each in their own context, there are others who insist on taking sides vehemently which is great because I enjoy watching/listening to the debates as there is always something to learn from each side of the argument.)