This is the provocative question asked, and at least partially answered, by Joshua Topolsky in this article from the Washington Post:
What’s interesting about this is that I didn’t know about any of these alternatives, with the exception of Bing. This is sort of a jarring realization for someone who is old enough to remember a time Before Google, when there were plenty of other search engines out there.
So, instead of googling something today, why not try blekkoing it or duckduckgoing it? You might be surprised what you find (and what you don’t).