What is the best advertisement network for web sites?

There are adsense,adbrite,cpmfun etc. Which one of them is best and why?

I assume for publishers? reports I have seen indicate Adsense generates the best revenue, I see cpmfun reviews suggesting it's the best paying, I was actually not familiar with that one, of course you need an entertainment site to qualify.
Second tier ad networks are typically for sites that can't get Adsense approval or operators who have lost their account.