It is true that big companies can pay to be near the top, Google also tends to 'know' so much about you they can tailor results to what they think you are searching for.
Sites with Google ads will often start showing items they know you have looked at.
It doesn't always make much sense though, for example if you buy a camera you aren't going to be much interested in all their ads for more cameras.

The other major search engine is probably Bing.com.
In the past Yahoo was OK but they seem to be losing the plot lately. 
Google is definitely best to be fair.