Google actually does give preference to Wiki articles. They give it more weight intentionally. As for the other stuff, it's not just the search I guess. You'd have to consider not only whether the results are good but what exactly is indexed as well. Some of these search engines may be good but their indexing depth is no match for someone like Google, Yahoo or Bing. Also, it's advertising $$$ that most of the search people spend. Weirdly enough, I read somewhere that Google doesn't advertise their search engine. I don't know whether this is only in TV advertising or something like that though.