Over the time, Google has removed list of competing search engines from its home page, that could be used if Google's results weren't very good. Here's an example from 2001:
Some addons are available to revive old Google feature: Customize Google is the most popular, a Greasemonkey script “Try this search on,” which lets you switch between different search engines. Google Matt Cutts points to another Greasemonkey script “Retro Links”.
Source:→ Google OS