What Makes A Product Successful?
Confirmation for my prejudices comes from a McKinsey study entitled Driving Growth in Consumer Products. It reveals that product launches that achieved above average success featured genuinely innovative products or repositioned products (one example was a Yoplait product that was aerated and successfully relaunched as a dessert).
By contrast, product launches that were not so successful tended to be line extensions (i.e. new flavours/sizes of existing product ranges) or products that competed on price.
Product is the first P of marketing. If you don't have the right product, don't start promoting it.