Good question. Actually I don't have any data for that. Anecdotally many "store brand" items of things that seem commodity-like, are things that I can get the same quality as a name brand at a lower price. This is better for me, and I suspect better for most consumers in a static situation. But the market is dynamic. Does this stifle innovation of new products? Does the reduced revenue of "brand" named producers, especially smaller ones hurt? Does the price competition produce a race to the bottom that ultimately doesn't benefit consumers? I don't know. But I would say that the considerations of increased regulations of "generics" vs increased regulation of "online markets" seem to me to involve different tradeoffs.
Sadly, the American grocery store is not optimized for consumers, so we can't draw many inferences from it. It's true that no-frills versions of commodity products are a good deal compared with heavily marketed products. But I don't see any reason to think letting individual stores dominate that market segment would be necessarily better for consumers.
