My pet theory is that the reason why every search engine is worse than Google is because they all use Google's interface. They want a single textbox capable of searching everything. Google spent who knows how much money in R&D perfecting this search box. You can't make a search box more perfect than what Google has. I'd even say that most problems of "bad search results" are directly caused by this minimized interface design.

I think alternative search engines would have better chances if they provided alternative interfaces to refine search queries instead of trying to compete with Google/Bing.