Apple has created a page on iTunes for the top app downloads of all time within the App Store. One of those categories includes the top downloaded apps within the free app category. Of the top ten free iPhone apps, two of them are from Google.
Yes, Google is dominating the App Store with the Google Mobile App and Google Earth taking up two of the ten spots in the top free app section. The only other possible Google competitor in that batch is Facebook, which is technically not a search engine.
Here is a screen shot: