There are plenty of counter examples to your claim: YouTube, Google Maps, Picasa, various companies focused on voice recognition and Google Glass, etc...

Google Glass? As far as I know, Google Glass is originally a Google X project ... they did not acquire a company if I know correctly. They hired some people from the wearable computing field.

Android, Google Analytics, etc etc etc

I’m not sure whether those are good examples. Android Inc wasn’t much of a company when they were bought by Google and the initial Google Analytics offering was very different from the service they bought (Urchin). Meanwhile, Google has killed over a hundred services in the last couple of years.

Apple has bought several companies that had shipping products and just like Google, Apple didn’t cancel those. Examples are FileMaker, Logic, and Final Cut Pro. After it bought PowerSchools, Shake and Astarte, it kept their products on for many years. Furthermore, it is often said that Apple’s acquisition of NeXT was a reverse takeover.

I can assure you any company anyone acquires will look very different 5 years from acquisition if its still alive.

Also, any startup not acquired should look very different 5 years from conception.