These sites are frequently criticized because nothing to differentiates their products from those of their competitors. It's easy for a consumer to decide which product to buy when there are clear differences between products. Try creating a difference in the mind of each customer.
Many factors go into making a purchase decision, and some carry more weight than others.
Consumers are frequently thought to buy products based primarily on emotional appeal. However, customers now research many types of consumer products on the web. Even low-priced products are being researched more extensively than ever before. A good example is toothpaste. It has gone from a commodity product with superficial advertising to promotions based on differentiation features that deliver specific benefits.