In Lisbon, there are a lot of supermarkets brands that are everywhere in the country and they all compete to have the lowest price. The big ones are Pingo Doce and Continente, with Lidl and Auchan right behind. Now, personally, I like more Continente, mainly because of their own products, which in portuguese we call them "White brands". However, the take away part of the supermarket is not the best there; for take away I usually go to Pingo Doce.
You can find these two supermarkets everywhere, and with very different sizes depending on the location (when you are in the historical part of Lisbon, usually they are very small and compact supermarkets; but as you go to the suburbs, you start seeing huge supermarkets - hypermarkets, as we call it - that have more products and more brands that you can choose from).