The two Aldis that I use in the UK are tidy and spotlessly clean. The company seems to have a good reputation for treating its staff properly.
I don't use Tesco if I can avoid it. They have a reputation for treating their suppliers very badly - instances of forcing the supplier to pay them in order to continue to be stocked in the stores - usually Tesco had wangled things so that they were the sole outlet for the supplier's product. This isn't hearsay - the BBC devoted a whole programme of Radio 4 to this issue, naming suppliers who had been driven out of business by Tesco's shenanigans! They also are (in)famous for paying their milk suppliers less than the cost of production after they have manoevered them into being sole supplier by giving them what looks like a good deal. Again information comes from reports from the BBC.
I like M&S. They are expensive but the quality's there so I use them for special occasions. I also use the Co-op regularly . Their goods and their ethics are excellent. They treat their suppliers well and are very big in Fairtrade with their own-label products and if the customer is a member we get "divi" - 5% of what you spend on their own-label products goes back to the customer and 1% goes to a local good cause of the customer's choice. Now THAT'S good business!
We also have ASDA which is part of the Walmart set up. I'd starve before I'd shop there.
As I said before, I'm lucky in that we have small independent food shops where I live. I also have doorstep delivered milk. It's distributed by a small local company which markets the milk on behalf of local farmers and pays them a reasonable cut. It comes in re-usable glass bottles too so no unnecessary waste for landfill.
I expect this all sounds incredubly quaint for all you sophisticated Yanks