Marks and Spencer was second, winning marks for store appearance and product quality.
Shoppers said Aldi stores were untidy and had rushed checkouts but forgave such shortcomings to save money.
But both Lidl and Aldi scored poorly for queuing time, staff availability and for the range of products on offer.
Meanwhile, Sainsbury's was at the bottom of the results of a survey of 6,800 shoppers by Which?
Consumer watchdog Which? has released its annual supermarket customer satisfaction survey, showing that after three years at the top of the foodchain Waitrose now languishes in fourth place - with Aldi reigning supreme.
Aldi fans loved the supermarket's "fantastic prices" with many also praising an "always improving" selection of food, Which? found.
The survey, conducted last October, asked customers to rate their supermarket shopping experiences in the past six months.
Some Aldi shoppers have got more than they bargained for in recent weeks, though; one customer reporting finding a rat in a bag of frozen vegetables, while in a separate incident a woman discovered a live stick insect in her salad. Home Products and Services.
Among the online supermarkets, Iceland came top for the third year in a row - a position in this year shares with Ocado. Iceland received five stars for its home delivery service, with shoppers pleased with the availability of delivery slots and punctuality of its drivers.
Iceland managing director Nigel Broadhurst said: "We are naturally delighted to have been recognised once again as Britain's best online store in the annual Which? supermarket survey".
As high inflation pushes prices upwards, customers have moved towards discount retailers - both Aldi and its rival Lidl have been growing quickly in the notoriously competitive United Kingdom supermarket at the expense of the larger retailers like Tesco and Sainsbury's.