I think it would be a good idea if Google changed their results around from day to day or even per search, showing different QUALITY sites at the top of the results. I get tired of seeing the same old mega-large; typically review sites and user created "submit an article" sites with little to no originality.
If Google never allows other quality sites, especially some of the smaller niche sites to take a top position in the serps, the results will eventually become stale and users will be forced to search on other search engines to find variety.
If potential webmasters feel that breaking into top search results is impossible, they may pass on creating a site which may add value to the web.
If you find a site you really like and you want to go there again, simply bookmark it.