Oh man, Civ dos, the original, is far better for the gamer that started with it.
the original (dos) has many little things that is lost in the windows versions.
First, the music of the different civs (zulu, mongol, etc..) is far better in the dos version and when you are used to them, the windows version will sound bizzarre and quite bland.
Second, there is the way the dos version automatically shows you the "view city" window when a city improvement (library, bank, wonder, etc...) is built in a given city. You don't get that "Stimuli" in the windows versions.
Third, the dos version has little animations on the map for rivers, you can see the flow of water moving.
These are the only three I can think of for now, but I am sure there are plenty.
The thing that made me ditch the windows versions though, is the sound. I wanted the original sound, and also the original feel of the game. I wanted that feel so much that I also ditched the idea of running it in dosbox (still had weird sound, not the original adlib ou sound blaster sound). I got a real old computer (pentium 066) with a real VGA monitor, nothing like having the true sound and even a monitor that has the right-sized pixels for well-cut VGA graphics. There you've got it for an original civ1 experience!
