To an extent (and in some cases, I except that there are exceptions) this holds true:
If I google for a video streaming website I want Youtube to be at the top of the list. Semantically that is the correct answer to the "question" implied by the search.
So:
Are google services popular because they are highly represented in google's search results?
-OR-
Are google services highly represented in google's search results because they are popular.
I absolutely do not believe that google should feel pressured to artificially demote its own offerings over fears of anti-competition litigation/legislation. On the other hand I can see an argument for clearly marking a result that points to a google service as 'belonging' to google.