I'm stunned there are still people about who haven't shopped at aldi before 
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The fish cakes, both specially selected and the "ordinary" ones are lovely though I can't compare to Lidl as I don't shop there.
The chocolate/crisps/biscuits are generally good as pps have said.
It definitely depends on the individual store but the fruit and veg in mine is really good. Not necessarily the Super 6 as those aren't refrigerated but you judge on the day.
Sliced bread, sandwich thins, pittas, part baked rolls, all good in my experience. Wraps - only the plain ones, the seeded ones have a weird vinegary smell and taste 
and the herbed ones weren't great.
We don't eat meat so can't comment on that but have had their fresh and frozen fish and we were happy with both. Also some of their frozen rice/veg bags - a lot cheaper than branded stuff and always handy to have in.
Deli stuff such as olives, dips, semi dried tomatoes, falafel etc. Most of their cheeses, yogurt and fruit juices.
I like their washing up liquid and dishwasher tablets, also the laundry detergent and fabric conditioner.
You'll find there are things you like and others you prefer a branded version but don't do that thing of assuming one or two not nice items means nothing else will be good! The stuff is made to sell under the aldi brand but it's all from various producers.