Google is staying ahead in search share because other search engines have not been able to create a product that’s better and different enough from than what Google supplies.  Many search engines may actually be better in some aspects, than Google, as a recent Businessweek article contents.

"Indeed, neither do analysts. Many say that despite the ease of switching to a new search engine, the new technologies are not different enough to draw users away from Google. "People don’t just go to Google because they can get the best search results," says Safa Rashtchy, a managing director at Piper Jaffray (PJC). "They also go there because they trust it. The technology would have to be massively more useful than the existing one to get people to switch. Theoretically it is possible, but realistically it is unlikely."

Just how much more useful would search need to be to unseat Google?   Well, Google, for all it’s power, is still text based in it’s algorithms.  If a company could create a Superior visual search engine that understood Rich Media and text, plus gave you a way to customize how you display the information - and did it quickly enough - it might have a shot of unseating Google.

But, realizing that, Google would probably build that capability before anyone else - further cementing their foothold into Search.   In short, at this time, it’s next to impossible to unseat Google.