In order I would opt: Morrisons Asda Tesco I feel that overall Morrison's has the best range of produce at the best value. Their customer service is also the best I have received out of the three top supermarkets. Asda has a great range of products are varied value. Not as good as it used to be or as they claim to be. Customer service is also varied have had some great customer service, but then on the other hand sometimes it has been severely lacking. Tesco is definitely at the bottom of the list because it is behind Asda and Morrisons in both department. A lot more expensive and staff are have less product knowledge in my experience. Don't shop at Tesco unless I have to.
