What is most important - a good product or friendly, fast service?

i think a good product is most important than the service

Good product indeed.

good product

If you go to a shop and find the product you want then you found the cashier smiling, friendly and dealing fast with payment process that will give you a good impression about that shop that you may go back again to buy from it.

It depends in product and service because there is nothing called pure product nor pure service both are connected somehow and important for customer satisfaction, but if it’s for long-term then the service need to have more features than the short-term, and for short-term the product need to be higher quality with acceptable price, that If you are searching for customer satisfaction.  

Cheaperbetterfaster always important, if not, a good product will be just as good.

The are both important. For some products, the products' value to the customer is more importnat. A good example for this will be the food products. For other products, the after sales services is more important. An example for this group is the software systems.

Often this comes down to price and demand. Fast and limited quality = cheap and high volume (Mc Donald’s).

Friendly and customer focussed service has nothing to do with this equation. If a service is not provided with the right service attitude then this would reflect a management issue or on a higher level a cultural problem within a company.

GOOD  PRODUCT AND FAST SERVICE -FRIENDLY ALL THIS  VERY  IMPORTANT

- To show the customer that they are getting a LOT of value for the product they’re buying.  By breaking each piece out,

- you’ve taken care to make sure your product focuses on the outcomes your customer wants to buy.

To be market leader one has to develop a good product which meets the customer requirements and customer feels delighted with the product, but to have long lasting impact on the customer and make the customer loyal one has to give a good after sales service too. As this helps in long term relationship and also helps in engaging with the customer. So I would say both go hand in hand .