I've seen searches with the first eighty (80!) results being shared amongst only three(3!) sites. Id say that removes what used to be 77 other sites from the first 8 pages of results quite nicely. The three are big brand stores, all well known already, and the 77 left out in the cold... who knows.
I've seen Google muscle in on content in a growing number of verticals including local and travel and they are expanding with well branded review sites as I type this.
I've seen Google smash what it deemed to be content farms while at the same time handing the biggest content farm out there a contract to create youtube videos for it, that company was Wall st backed of course.
I've watched as Google virtually eliminated any competition from the affiliate and online shopping niches, left them all to fend for their own traffic while it promoted its own shopping portal heavily.
I've watched Google fear social, twitter and facebook so now all roads lead to G+, MySpace wasn't big enough anymore.
How and why? One word, business. The internet is for business according to Google, the business of owning it and showing ads on it. Their ads, not yours, on their pages if they can manage it.
Is Google still a good search engine? The title of this thread gives you the answer. On a scale of zero to ten I'd give the current iteration of Google search the exact same score you see in that little +1 button below.