there is no single great antyvirus, i tellyou this because i personally ran tests on an infected machine,
I tested the exact configuration with avast,nod32,mcaffe,norton, and kaspersky, and each one would detect viruses that the others wouldn't , (all of the antivirus engines where the latest ones)
althoug i would have to say that Kaspersky and Avast prove to be the most effectife thoughh