The vast majority of search engines show ads based on search results, users expect adverts as search engines generally have to make money at some point.
Just tried a search (from UK) for same product on Google / bing (usb stick related)
Obvious on google results when something is sponsored / advert. - no attempt to fool you.
Similar if I choose bing search engine (albeit more ads).
The (non advert) results on 1st page from both quite similar - listed in order
Google: currys, amazon, argos, ebuyer, mymemory, maplin, wikipedia, 7dayshop, tesco
Bing: pc world, argos, ebay, amazon (twice - appears later in results too - in addition also has a sponsored ad), tesco, maplin, wikipedia, mymemory, ebuyer
So Bing gave 1 more result (but Amazon twice), majority of "hits" similar, noteable that google did not give ebay - however ebay was there as an advert. Should be noticed ads on both quite similar.
With either of these "major" search engines I would have to refine search / go through several pages of results to get to more obscure retailers - which is what I expect from a search engine: I expect big companies / specialists
Essentially I get same user experience with a major Google competitor as with Google, so really do not see the point of the complaints - presumably similar algorithms used by both search engines.