Google is not presenting their own competing services in a biased way over others. They are presenting search results in context sensitive ways. Searching for sushi in a geographic location indicates you want to find sushi places in that area. A google map is the best possible way for google to present the information you want. Does a crowdsourced site completely dedicated to this tiny niche do a better job than goog…
if google is a search provider mapquest or other map engine results should have been there like it does web content from yahoo or microsoft.