The early search engines (Webcrawler, Lycos, ...) ranked "relevance" based on some silly metric like "the more times the search term appears on the page, the more relevant the page must be".

So the result was that the first pages were full spam sites that just used search terms as hidden text. Then Altavista came and it was a huge change for the better. They at least made some effort of trying to rank actual relevance. Of course, Page/Brin's invention that made Google what it is today is PageRank, and none of the competition were close to an idea that good.

So PageRank'ed pages, good spam detection filters and ads on the side = Good Google. A search engine that stood out against the competition.

Now Googlee has horrible site spam detection, shows ads in the main result list (some times it's all you see). Google now has very little edge against the competition. Even just 1-2 years ago DDG and Bing were a lot worse than even the modern day Google. But what should make the search people at google really sweat isn't so much that google has deteriorated a bit, but that Bing and DDG have improved so much that they are now on Par. Google search has never had peers at any point since it was launched.