New Coke was a wildly successful strategy by Roberto Goizueta to 1) Reignite the public's love of Coca-Cola (taking it off the shelves for three months), while at the same time 2) Reformulating "Classic" Coca-Cola to use HFCS which tastes slightly different from the sugared version. It was such a ballsy and creative move, I can hardly believe it really happened.

Betamax was technically superior to VHS, and was at the center of a Supreme Court case that ruled home recording to be fair use. It lost out to VHS in the marketplace for various reasons, so it's a good case study of a business failure for sure, but not because the product was bad or ill-conceived.