Yeah, it's weird but at some point I stopped liking Coke (or any carbonated beverage). In college I would drink 2-3 cans per day and now I'm drinking like 2-3 cans per year. I don't remember making an actual decision to stop drinking it... it just gradually happened. And now I don't really like the flavor.
Another think on the same point as the OP, is that Coke's flavor seems to vary around the world. Definitely Coke in Europe tastes different than Coke in the US - I think it was the use of sugar beets in the EU and corn syrup in the US but I never was sure. It's not that one is more sweet than the other - although I think the EU version is slightly sweeter, but the EU version tastes different. In a blind taste test, I am certain that I could always figure out the US coke - they are very different.