Gmail is hard to replace because it's well integrated with other Google services, in particular Google Apps with its own ecosystem.
Google Search is hard to replace because of the quality. Bing is ok but not close in quality.
For the privacy-conscious, Dropbox is saddled with the same pitfalls as Google and Facebook, unfortunately.
> Google Search is hard to replace because of the quality. Bing is ok but not close in quality.
https://disconnect.me/search used to show Google search results, but it looks like Google has blocked it for the time being.
I personally use https://duckduckgo.com/. The quality of results is definitely below Google, but I believe that'll only improve as more people switch to them.
I know it's totally not perfect, but is it logical?
I can type 'Fall Photos' and instantly see all my fall photos taken in the past 5 years.