People's probelm with 3D graphics is that Civ3 worked fine with good (i.e. pseudo-3D) 2D graphics, the fact that they will be 3D is not obvious, Civ3 gameplay has no need, and is not enhanced in any way other than aesthetics (which I admit is important, but Civ3 looks pretty good as it is). If there was no downside to 3D graphics then obviosly we wouldn't object, but there is - any game with rendered 3D graphics is going to require more processor power and bigger graphcis cards, and when its really unnecessary for Civ, then this just seems like a waste, I like the fact that Civ3 can generally play pretty fast on most machines, I don't need better graphics, nor do most Civ players, so why should we give endure longer loading times, the need for better graphics cards and greater processor usage to get them?
Improved graphics are fine, excellent even, but I would focus them on a more aesthetic interface generally, not a 3D rendering game engine. But above all I would like to see a more intelligent, more devious, more REASONABLE (a not often stated weakening effect of more intelligent computers) and more strategic AI.