I for one don't like Blizzard's graphics, except for Diablo II. Warcraft looks too cartoonish, and Starcraft 2 also seems to have a non-serious look to it. World Of Warcraft is way too cartoonish for me.
And I don't like comic books or comic book art.
So basically I don't want my games to feature that sort of art. Especially Civilization. Civilization to me is the complete opposite of a "cartoonish" game, or should be. It used to be, but lost it's way with Civ IV. Cartoonish works for games like The Sims, Worms, etc. But for games like Civilization you need as realistic (or "serious") graphics and art as you can get.
Personally, totally realistic sound effects are a bit more important than totally realistic graphics, because realistic sound is much easier to achieve (in fact totally realistic graphics are still impossible) and thus the sound can enhance the semi-realistic graphics and still give you that illusion of total realism. Hope that makes sense!
Imagine Rome: Total War or Medieval 2: Total War with cartoonish graphics. You'd completely lose immersion in the game, or at least I would. Those two games aren't totally realistic, but they do a good enough job steering towards the serious and away from the cartoonish, plus the addition of realistic sound effects, that the total effect is successful, realistic, and immersive. Why can't Civ do the same? Or the real question: Why did they choose for Civ to not do the same?
Yep. Sometimes I just feel like two floating eyeballs and a grinning mouth, with a blue feather headdress and neckband. Really. It usually happens when I'm dehydrated.