If you read this comparison between Wikipedia, Yahoo and Google, you should understand why i think Wikipedia beats all these other sites.

The text below is from the Wikipedia Site so it might be biased...but

From Wikipedia founder Jimmy Wales

Google might have close to a million servers. Yahoo has something like 13,000 staff. We have 679 servers and 95 staff.

Wikipedia is the #5 site on the web and serves 450 million different people every month – with billions of page views.

Commerce is fine. Advertising is not evil. But it doesn't belong here. Not in Wikipedia.

Full read:

https://donate.wikimedia.org/wiki/Special:FundraiserLandingPage?uselang=en&country=KE&template=Lp-layout-default&appeal-template=Appeal-template-default&appeal=Appeal-default&form-template=Form-template-default&form-countryspecific=Form-countryspecific-control&utm_medium=sitenotice&utm_source=B11_Donate_Jimmy_Control&utm_campaign=C11_1107_AFRICA