Corn syrup is probably why I stopped drinking Coca-Cola and switched to (aspartame) Diet Coke. It just didn't taste as good, though in recent years I've heard that may be because its flavor is more temperature-sensitive, and aspartame isn't. (Then I gave up DC so I wouldn't have to maintain a consistent caffeine dosage to avoid headaches, but I do get CFDC in the gold cans from time to time.)
But I also liked the original formula (with sucrose), enough that I could tell the difference in an unexpected blind test. When "New Coke" was about six months old, my mom took me along to a car repair place. They apparently were big on buying sodas by the case. I opened a can of Coca-Cola, took a sip, my eyes got big, and then I noticed the promo offer on the can from just before New Coke. Supposedly switching to HFCS was in fact not the motivation for making New Coke, it just happened to be at the same time.